RFCs are relatively easy to find on the Internet. Many companies and educational institutions maintain complete local repositories of RFCs, so you should check for such a local repository that may be convenient to you.
When the IETF announces an RFC, primary English RFC repositories already have the RFC. The following URLs are paths to primary repository directories. The English versions are authoritative. Their directories have a file for each RFC with a file name of the form "rfcnnnn.txt: without leading zeros for example, rfc2821.txt or rfc792.txt. If the file is also available in Postscript or PDF, a version of the file will exist with a ".ps" or ".pdf" suffix.
The documents for "standards-track" RFCs that is, those in the Proposed, Draft, or Internet Standard state (or later in the Historic state) do not contain any indication of their state. Rather, they just say that they specify a standard. As a consequence, their state can be changed without reissuing the RFC: RFCs are never changed or reissued, although they are sometimes made obsolete by a subsequent RFC. You can consult the "rfc-index.txt" file for the status of any RFC, including whether it has been modified or made obsolete by a subsequent RFC. This file is found in the same directories as the RFCs.
Some search facilities and pointers to other RFC sites are also available on the RFC Editor Web site [RFC Editor].