Always verify the revision number on the cover page. If it doesn't say "IPC-7801A," it is obsolete.
If you are hunting for the IPC-7801 PDF , you are likely looking for the industry blueprint on keeping your reflow ovens in check. Formally titled the Reflow Oven Process Control Standard ipc7801 pdf
In all these cases, a certificate of compliance referencing is often required by the end customer. Always verify the revision number on the cover page