Any way to have a PDF tagging system?

Directory Opus is by far one of my most used programs and I would love it if it could streamline my work flow even more by letting add tags to PDF files. I realize that PDF files don't inherently allow for this type of metadata but perhaps it could be accomplished through XML files or other similar solutions.

I'm a teacher who works with MANY important documents and it would help me greatly if I could tag my PDFs like I do my photos. For example, a reading document could be tagged with "shakespeare," "reading methods," and "discussion ideas."

If DO can't do this, does anybody know of ANY programs that enable the tagging of PDF documents? I know that I can now tag my microsoft docs in Vista but I have WAY more PDFs than DOCs. I'd appreciate any ideas in this matter.

You could use the descript.ion system built into Opus but that wouldn't allow you to sort on different tags - only on the complete description.

Better than nothing perhaps.

Adobe Acrobat Professional does allow adding key words to the PDF documents. It has a high price tag, though. There are other (much cheaper) alternatives for the Adobe Acrobat but I don’t know their possibilities WRT tags.
Toller

[quote="Toller"]Adobe Acrobat Professional does allow adding key words to the PDF documents. It has a high price tag, though. There are other (much cheaper) alternatives for the Adobe Acrobat but I don’t know their possibilities WRT tags.
Toller[/quote]

I've seen the keyword system but is there any way to filter through keywords like one can do with image tags? I haven't seen much use for the keywords yet unless I'm missing something entirely.

Maybe this one? Has command line equivalent, as well:

sharewareup.com/visit.php?vid=155&pid=10390

While Dopus AFAIK does not support showing “Keywords” column in the details view, in the Windows Explorer you can right-click to mark the “Keywords” column to show up.
Toller