The web is filled with stuff about PDF and Acrobat. Below are some of my favorites. Add a comment at the bottom of the page to let us know about your preferred resources.
Web sites about PDF
PlanetPDF and the PDFzone are the two leading web sites regarding the use of PDF in a prepress environment (well OK, some folks may say that Adobe also has something to say on the subject). They both offer guest writers, well written pieces, information on new products and links to other sources of information. The same is true for 4xPDF, a fairly new initiative. German PDF-lovers can also take a look at PDF-zone.
Both PlanetPDF and the PDFzone maintain an extensive list of PDF tools so I am not going to bother doing the same. Here are just the 3 plug-ins every prepress company should have:
Quite Software has some pretty cool Acrobat plug-ins like Quite-A-Box-Of-Tricks, a toolbox that is great for manipulating PDFs coming from Office applications.
Enfocus is a Belgian company that created Pitstop, a plug-in to flightcheck and correct PDF files. It is a nice tool but stay away from any of their .0 releases.
CrackerJack is an Acrobat plug-in to print PDF files to a RIP the prepress way, meaning with crop marks, user defined screen angles and all the other goodies you expect.
Mailing lists & forums
I guess the best PDF-oriented forum you can find nowadays is the Adobe one.
I also like the Apogee Network, a mailing list specifically for users of the Agfa Apogee workflow.
Books on PDF
There are nowadays tons of books about PDF. The ones I read are too outdated but there is one classic that still is worth mentioning:
PostScript & Acrobat Bible
This is an excellent book by Thomas Merz describing both PostScript and Acrobat from a practical point of view. Unfortunately it only covers PDF up to version 1.2 (Acrobat 3). An updated revision appeared around 2003 but this new version is unfortunately only available in German.
ISBN 3540608540 – Price: $69.50