Best Practices for Creating PDF Files

Most people who create PDF files never get beyond the basics. In fact, they don't need to, because Creative Suite applications provide PDF presets (settings files) that do all the heavy lifting. But if you spend a lot of time working with PDF files, it's helpful to learn a few "best practices" for customizing your PDF files and PDF presets and really mastering PDF file creation. These best practices include choosing the most appropriate compatibility settings for the intended output, compressing files, deciding when to embed fonts, and handling color.

In this chapter, we can focus only on a few key issues. For more details, we recommend looking at two Adobe white papers Adobe InDesign CS2 Printing Guide for Prepress Service Providers and Adobe Acrobat 7.0 Printing Guide, both found on the Creative Suite installation CDs (see "The Extras" section in Chapter 1 for the location).

Setting Appropriate Compatibility

The Compatibility options control which versions of Acrobat viewers can open PDF files as well as support for such features as transparency, layers, the blind exchange of print-ready files, and encrypting documents for security. (See Table 14-2 for more information.)

Table 14-2. Acrobat and PDF Compatible Features
Compatibility/PDF Version	Acrobat 4.0/PDF 1.3	Acrobat 5.0/PDF 1.4	Acrobat 6.0/PDF 1.5	Acrobat 7.0/PDF 1.6
Viewers Able to Open PDF File	Acrobat 4.0 and later	Acrobat 5.0 and later	Acrobat 6.0 and later	Acrobat 7.0.
Transparency Support	No: transparency flattened.	Yes, when directly exported from CS2 applications.	Yes, when directly exported from CS2 applications.	Yes, when directly exported from CS2 applications.
Layers Support	No	No	Yes, from Illustrator and InDesign	Yes, from Illustrator and InDesign
PDF/X Support	No	No	PDF X/1-a and PDF X/3	PDF X/1-a and PDF X/3 (including newer versions of the PDF/X standards).
Encryption Support	40-bit	40-bit	40- and 128-bit	40- and 128-bit

These options are available when directly exporting PDF files from InDesign, Illustrator, Photoshop, and GoLive (which we'll refer to as "the CS2 applications" in this section); and in Distiller. Choose from these options in the Compatibility pop-up menu:

In the CS2 applications, in the Export Adobe PDF dialog box (see Figure 14-2), choose Acrobat 4, 5, 6, or 7 from the Compatibility menu.
In Distiller, after choosing to edit a settings file (choose Settings > Edit Adobe PDF Settings), click the General panel and choose Acrobat 3.0, 4.0, 5.0, 6.0, or 7.0 from the Compatibility menu (Figure 14-6).

Figure 14-6. Set Compatibility for Distiller in the General panel.

Here are some general recommendations for setting compatibility:

To retain transparency in a file, choose Acrobat 5.0, 6.0, or 7.0 compatibility.
To flatten transparency, choose Acrobat 3.0 or 4.0 compatibility.
To retain layers created in Illustrator and InDesign, choose Acrobat 6.0 or 7.0 compatibility.
To create PDF files for a sophisticated audience of graphic professionals (who likely keep their version of Acrobat or Reader up-to-date), choose Acrobat 6.0 or 7.0.
To create PDF files for the widest possible audience, save with Acrobat 4.0 or 5.0 compatibility.

Exchanging Files "Blindly": The PDF/X Standard

To reduce printing errors in PDF files and enable the successful exchange of files, Adobe joined with other vendors and professional users to develop the PDF/X standard. This standard was designed for the blind exchange of final, print-ready PDF files. It aims to eliminate common errors in a document, such as missing fonts and images, or incorrect color spaces. PDF/X makes it possible to deliver files ready for print production to nearly any print service provider with confidence that they will print as you intend.

It might be appropriate to use the PDF/X format when creating a file, for example, that you'll send to a magazine or newspaper when you aren't communicating directly with those who will output the file. Some commercial printers now request that customers create PDF/X-compliant PDF files. Consult with your publisher or printer to determine whether selecting a PDF/X preset is appropriate for your project.

The PDF/X standard is actually a family of ISO (International Standards Organization) standards, available as PDF presets (settings files) in Acrobat Distiller and the CS2 applications. A subset of the Acrobat 4 (PDF 1.3) specification, the PDF/X format requires that transparency be flattened, fonts be embedded, appropriate PDF bounding boxes be specified, and color appear as either CMYK, spot colors, or both. PDF/X-compliant files must also contain information describing the printing condition for which they are prepared. You can choose from two options:

PDF/X-1a supports CMYK and spot colors only, but doesn't allow color management. This standard is more commonly used in North America. Choose this option when you're sending digital ads to be reproduced on a press characterized to a printing standard such as SWOP (Specifications for Web Offset Publications) or SNAP (Specifications for Non-heat Advertising Printing) or when you want to maintain absolute control over a file's content and color appearance.

PDF/X-3 also supports device-independent color and color-managed workflows. This standard is more widely used in Europe. Choose this option for complete files that you will send to digital presses or other color-managed environments, where you expect the printer to optimize color reproduction for the specific printing environment.

Downsampling and Compressing Files

Downsampling and compressing a PDF file can significantly reduce its size with little or no loss of detail, and can speed downloading. (Downsampling means reducing the resolution of an image.) To customize downsampling or compression, in the CS2 applications, use the Compression panel of the Export Adobe PDF dialog box; in Distiller, use the Images panel (Figure 14-7).

Figure 14-7. Resolution and compression settings in CS2 applications (left, showing InDesign) and in Distiller (right).

Two kinds of compression lossy (JPEG) and lossless (usually ZIP) can be applied to images in PDF files. Lossy compression will degrade quality somewhat, especially at low quality settings, but may not noticeably affect quality at higher settings. Choose Maximum or High Image Quality for press or print. For an important project, do visual tests to see what works best for your intended result.

Always determine resolution according to the intended use of the PDF file: For commercial printing, usually downsample images to 300 ppi. For best results for desktop printing, use a downsampling value between 150 and 200 ppi. For onscreen or web images, use a range between 72 and 100 ppi.

Embedding Fonts

Given the choice, it's almost always a good idea to embed fonts. That way, anyone viewing the PDF file, regardless of their platform and whether they have the original font, will be able to see it, and print it, exactly as you would.

Choosing to Embed Fonts

You can choose how fonts in a PDF file are handled in CS2 applications using the Advanced panel, and in Acrobat Distiller using the Fonts panel (Figure 14-8). In the CS2 applications, fonts are always embedded. In Distiller, to embed fonts, check the Embed All Fonts option.

Figure 14-8. Set PDF font options in a CS2 application in the Advanced panel (left, showing InDesign), and in Distiller in the Fonts panel (right).

Tip: Detect Embedding Restrictions

Some fonts can be restricted by their font foundry to prevent embedding, editing, or both. InDesign can identify those using its Preflight feature. Distiller will show an error in its message log when a font cannot be embedded.

Tip: Embed Fonts in the PostScript File Before Distilling

If you're creating your own PostScript files, be sure to choose the option in your printer driver or application to embed the fonts in the PostScript file. It's impossible for Distiller to embed the fonts in the PDF file from the converted PostScript file if it can't find them!

Subsetting Fonts

Whether to create a subset of fonts can be a complex decision. Subsetting stores only the characters actually used in the PDF file, not all the glyphs in the font. Subsetting has two purposes: To keep the file size down, and, more importantly, to prevent font substitution when a file is printed on another system. Subsetting is generally a good idea.

Distiller can specify a threshold percentage below which it embeds only a subset of the fonts (using the Subset Embedded Fonts When Percent Of Characters Used Is Less Than option). For example, with a threshold value of 35, if more than 35% of the characters are used, Distiller embeds the entire font. To ensure that Distiller subsets all fonts, enter a value of 100%.

In the CS2 applications, an equivalent option (in the Advanced panel of the Export Adobe PDF dialog box) defaults to subsetting at 100%. To turn off subsetting, set the threshold to 0%.

For some special fonts, such as dingbats or pi characters, Distiller may fully embed the font regardless of the subset value entered, to ensure that the proper characters are used when the PDF file is viewed and printed.

Handling Colors in a PDF File

The color settings for working with PDF files are quite complex. They specify how to represent color information in the exported or distilled Adobe PDF file. For example, if the original file used a mixture of RGB and CMYK objects, the color settings can control how the RGB objects are converted to CMYK upon export. All spot-color information is preserved during color conversion; only the process-color equivalents are converted to the designated color space.

We recommend that you read Chapter 10, "Color and Color Management," for an overview of color issues in the CS2 applications. The most important settings are Color Conversion in the CS2 applications and Color Management Policies in Distiller (Figure 14-9).

Figure 14-9. Choose color settings when creating PDF files in the CS2 applications Output panel (left, showing InDesign) or in the Distiller Color panel (right).

In the CS2 applications, you have three options for color conversion:

No Color Conversion will retain the color spaces of objects in the document, without conversion.
Convert To Destination will convert objects with embedded profiles from their source profiles to the destination profile, and objects without profiles from the document working space to the destination profile. This option can be useful for converting RGB images as you export to PDF.
Convert To Destination (Preserve Numbers) will convert objects with embedded profiles from their source profiles to the destination profile. The original CMYK color values of objects without profiles are preserved. (This is the default setting for the Press PDF preset and is preferred for a commercial printing workflow.)

In Distiller, you can choose from five color management policies:

Leave Color Unchanged will not change device-dependent color spaces (RGB, Grayscale, and CMYK) and preserves device-independent colors.
Tag Everything For Color Management (No Conversion) and Tag Only Images For Color Management (No Conversion) embed an ICC profile when the PostScript file is distilled. These two settings also convert RGB, Grayscale, and CMYK to device-independent color spaces.
Convert All Colors To sRGB converts RGB and CMYK images to sRGB. This makes the colors device-independent.
Convert All Colors To CMYK converts color spaces to DeviceGray or DeviceCMYK. This is preferred in a print-production workflow because it can convert RGB to CMYK. (This is the default for the Press Settings file.)

Exporting Extra PDF Features

In InDesign and Illustrator, you have options for exporting extra features that can be saved with a PDF file, as follows:

In InDesign, you can create Tagged PDF. We discuss this in the following section, "Editing PDF Files and Their Elements."
In InDesign, you can include bookmarks, hyperlinks, and interactive elements. See the following section, "Adding Interactivity to PDF Files."
In InDesign and Illustrator, you can save top-level layers. See "Moving Layers to PDF Files" in Chapter 12, "Layers."

Creating and Saving Custom PDF Presets

You can create and save customized preset files to call up specialized settings with a single click, to move them to another workstation, or pass them on to colleagues for their use. You might also get a preset from your print service provider to enable you to create PDF files the best way for the provider's workflow. (We discuss more about this in "Working with a Print Service Provider" in Chapter 16, "Preflighting and Printing.")

Choose from the following options to create and save a custom PDF preset file in the CS2 applications or a custom settings file in Distiller.

In the CS2 applications, choose either File > Export or File > Save As. In the Export Adobe PDF or Save Adobe PDF dialog box, start with one of the default settings, and customize the settings for your needs using the guidelines in "Best Practices for Creating PDF Files." Then click the Save Preset button at the bottom of the dialog box. Give the preset a meaningful name in the Save Preset or Save dialog box, and click OK or Save.
In InDesign and Illustrator, choose additional options for editing, importing, and exporting PDF presets. In InDesign, choose File > Adobe PDF Presets > Define; in Illustrator, choose Edit > Adobe PDF Presets. Use the Adobe PDF Presets dialog box (Figure 14-10) to view a preset's description, look at a summary of its settings, rename and delete presets, and load and save preset files.

Figure 14-10. In InDesign or Illustrator, use the Adobe PDF Presets dialog box to load and save PDF preset files.
In Distiller, create a custom PDF Settings file by opening an existing file. Choose Settings > Edit Adobe Settings File. Then make changes using the guidelines in "Best Practices for Creating PDF Files." Click Save As and enter a new name for your file.

Tip: Locate the Extras Presets Folder

Preset files for Rich Content PDF (for creating enhanced PDF in InDesign) and for the newer PDF/X-1a:2003 and PDF/X-3:2003 standards are included in the Extras folder created when you install Acrobat. (On the Macintosh, the path to the folder is Library > Application Support > Adobe PDF > Extras. In Windows, the path is Documents and Settings > All Users > Shared Documents > Adobe PDF > Extras.)

Custom preset files in CS2 applications and Distiller are saved with the .joboptions extension, in the same location as the default preset files, to make the new PDF preset available to all members of the Adobe Creative Suite 2:

On the Macintosh, the file is stored at:
Library > Application Support > Adobe PDF > Settings.
In Windows, the file is stored at:
Documents and Settings > All Users > Shared Documents > Adobe PDF > Settings.