If your intended output is a printing press, Acrobat offers a wide array of tools to make sure your final files print the way they should. These tools are grouped in the Print Production toolbar. Let's take a look at what each of these can do for you.
Because of the way inks are applied when printing color in an offset preset and because of the elasticity of the paper stock used for print, sometimes a thin gap may appear between two areas of different colors. To avoid that from happening traps are applied. Traps are very thin lines of overlapping inks applied to those critical areas to prevent these gaps from appearing. To create a trap, normally the area of the lightest color is slightly expanded to fit under the area of darker color. Acrobat files can contain specific information that enables printers to generate traps automatically when sending a job to press. The default Trap Presets contain generic values for the automatic creation of traps for most cases, but sometimes a job requires these values to be changed. Acrobat gives you the flexibility not only to change these default values but also to save them as a recorded preset. If you have doubts about setting traps, consult with your printer or service bureau. Most printers prefer to do the trapping themselves, so most of the time you should not worry about trapping. However, if you are producing your own color separation films, these trap settings are available to you. Settings may vary depending on the particular characteristics of the paper and inks to be used (see Figure 44.6). The available settings are
Figure 44.6. You can customize your trapping preferences and save them for future use.
The Output Preview feature enables you to see how the colors will break when producing separations and is for reference only. The preview doesn't display traps or halftone screens, and it shouldn't be used for proofing but only as way to check on the amount of ink coverage on the printed page (see Figure 44.7) or to spot any overprints quickly (see Figure 44.8).
Figure 44.7. Use Output Preview to see how each color plate will print and to check the amount of ink coverage. Too much ink can result in excessive moisture and cause paper to break when passing through a press.
Figure 44.8. Output Preview also displays overprint areas. Because inks are not entirely solid but have transparency to them, overprinting can result in big color variations in the final product.
If you are reviewing a PDF file created by someone else, you can have Preflight generate a report in text or PDF format that you can use for reference (see Figures 44.9 and 44.10).
Figure 44.9. Preflight comes with many profiles to help you spot and correct problems before sending the file to production.
Figure 44.10. Use Preflight's reports to correct problems before files are sent to a commercial printer for production.
Sometimes, due to time constraints or because the document has just too many images that need to be converted from one color mode to another, you may want to do the conversion with one click. The Convert Colors dialog is there for you. It is a no-nonsense way to straighten colors across a document quickly, especially if it's a long one (see Figure 44.11). It gives you options for three types of images: RGB, CMYK, and grayscale. You select the intended output and Acrobat converts the images. Keep in mind that this tool does not magically retouch and correct color. If an embedded image is of poor quality there's nothing that Acrobat can do about it.
Figure 44.11. The Convert Colors dialog is a quick way to change color modes to images all across a document or on selected pages.
Because the cost of reproducing a job increases with the number of inks required, you can also use the Ink Manager to reduce the amount of inks by mapping an ink to another. There are times, for example, when an artist may have chosen two slightly different spot colors when only one was needed. By mapping one of them to the other in the Convert Colors dialog (using the Action pop-up menu), you tell Acrobat to create one separation plate for both rather than two individual plates (see Figure 44.12). After color has been mapped to another, it can't be reversed to its original.
Figure 44.12. Use the Ink Manager to change ink density, trapping order of inks, or to alias one ink to another.
The Ink Manager is a fast way to preview how many inks are going to be required to reproduce a job. This is of special importance when working with spot colors since the cost of reproducing a job increases with the number of inks required. If you need to reduce the amount of inks used in a job but don't want to map similar inks, you can use the Ink Manager to alias one ink to another (see Figure 44.12). Aliasing inks produces the same result as mapping but, unlike mapping, it doesn't alter the images in the PDF.
The Ink Manager also enables you to change the trapping sequence of inks (the order in which inks are printed in a press). Because inks are not entirely opaque but have varying degrees of transparency, the order in which they are printed can make a difference to the final look of your printed document, especially in trapped areas.
Add Printer Marks
Printer marks are markings placed on film, outside the actual print area, that help printers by identifying what plate should be what color, the positioning of the page, the name of the job, registration marks, and so forth. Without printer marks a printer would be clueless as to what to do with a piece of film after it's produced. Acrobat can generate these printer marks automatically based on parameters you feed it in the Add Printer Marks dialog (see Figure 44.13).
Figure 44.13. The Add Printer Marks dialog.
What happens if the page size in Acrobat is not the final page size intended? A page in Acrobat could contain bleed areas or be a two-page spread, for example, in which case autogenerated printer marks would be placed in the wrong places. In situations like that, the Crop Pages dialog enables you to set up margins to define the exact size the finished product should be.
The crop box is the area that the final product will be and it is the area that the printer marks will frame. The trim box represents the actual size of your PDF page. The bleed box is the area that will be printed outside the trim box when there are bleeding objects or images (a bleed is when a page is printed all the way out to its edge). The art box (or media box) is the size of the page as it was exported from the application that created it (see Figure 44.14).
Figure 44.14. The boxes in the Crop Pages dialog.
Fix Hairlines is a straightforward feature. If there are any thin lines in the PDF that are part of text strokes or part of a vector object, Acrobat makes sure that they're not too thin and bumps up their width so that they show when the document is printed. Acrobat uses the parameters you supply in the Fix Hairlines dialog to accomplish this.
If your document contains overlapping raster images with transparency (like embedded GIF or PNG images), Acrobat flattens them at print time. However, if your document contains overlapping transparency vectors, Acrobat breaks each transparent area into pieces of solid (flat) color that can be either new vectors or rasters. You can determine how much of these transparent areas are converted to rasters or vectors using the Transparency Flattening feature and its Raster/Vector Balance slider. The lowest setting produces all the areas to become rasters, and the highest setting makes them all vectors. You can also determine the resolution of these generated rasters.
The vector/raster conversion is important if you are concerned about file size. Converting all transparent areas to raster produces larger files, and having Acrobat generate too many small vector images adds an extra demand on processing to the RIP or printer, which can translate to a longer processing time.
The PDF Optimizer dialog has several panels with options to clean up your PDF and make it smaller and easier to transport. Clicking on the Audit Space Usage button generates a report telling you what elements use how much space and their percentage in relation to the entire file size. After you have edited these settings you can save them for future use:
JDF Job Definitions
Job definition files (JDFs) are small files that can be attached to a PDF and contain information, such as number of copies to be made; the type of stock to be used for cover, body, and any other special sections in your document; the person to contact; billing information; a preflight report; and more. The job definitions are saved in a file of JDF format that you can reuse in future jobs (see Figure 44.18).
Figure 44.18. Job definitions contain all the information required for a printer to reproduce your document in a press environment.
Show/Hide Print Production Toolbar
Choose Tools, Print Production to toggle between showing and hiding the Print Production toolbar.