Need document management software that will allow me to do the following:

1. Documents are either in existing PDF format or will be scanned in
to one or more files.

2. Operator will able to tag each document with certain fields that
would be accessed thru a drop-down menu that can be populated with
client names & modified as needed. Additional drop down menu for
document label - e.g., 2004 Tax Data, Correspondence, Bank Statement.
At least 1 additional field needed for free form description.

3. Each tagged document will produce audit trail - date entered, by
who, assign automatic date & document #.

4. Can search all documents for specific words.
 
5. I have Windows Server 2003, 20 workstations w/XP. Price range under $5,000.

Have a look at www.zope.org combined with something like
www.plone.org. You will end up doing some coding or having it done for
you, but it should be well beneath 5000$

http://www.sentryfile.com/

This is a document management system. For the prices you'll have to
contact them, but it will be far beneath $ 5000.

An alternative is:

http://www.z-software.com/

It is less expensive and can do what you want it to do.

I work for a large in engineering company, we use a software program
called document locator, produced by Columbiasoft. Due to the many
purchasing options I don't know what price you would be able to get it
for, but it is definitely worth looking into, the software has helped
us organize our legal descriptions, and engineering files along with
CAD files and other documentation.  We can also relate all of our
research to the project's every project has a folder and which we can
be put with correspondence emails and any other documentation that is
required.

And because of its extreme compatibility with Microsoft compatible
programs we have been able to link values the project and document
profiles to a G I S system which gives us geographical information the
document that we?ll have searched, and the search capabilities are
extremely good.

This software has literally saved our company hundreds of man hours in
organization.

http://www.documentlocator.com/productinfo/