It depends on whether that Access-based program has a web interface or you literally have to manipulate it through Microsoft Access. If the latter, the Viewsonic VPad is your only real option and it isn't a very good one. The battery life is bad. In short, the market hasn't quite caught up to what you're trying to do here. Any current option isn't going to be all that fulfilling.
P.S. Ugggh, why in God's name would you routinely edit a PDF? That's the exact opposite of what that filetype was intended for. I don't mean to rant towards you, since I doubt it was your choice. I'm just lamenting the ever-more common love of using PDFs in cases other than sending something to print.
Edit: Wow. I've never even heard of this Motion Computing stuff. This is all way over the budget I'm familiar with, so I won't be of any help here. Desktop GUIs in a tablet form-factor never work out though. In my opinion, the ARM-based tablets with proper GUIs will be blowing that clunky x86 crap out of the water in 2 years for less than half the price.
I'm not sure if it's web based. I know it's ran through our server, other than that I really don't know enough about Traverse other than they have over a million in the software and it's limited and sucks, especially considering the growth of our company, it's just not a good set up for our facility and instead of dumping it they insist on trying to make it work by have 2 full time programmers who can't seem to get anything completed on time.
http://www.notforprofitsoftware.com/Traverse.htmlink to more info specific to this junk above.
As for PDF's it's required for us to provide files for FDA regulations due to being a medical device facility, especially in my role as the Quality Manager I have to enforce document control, with the PDF's I can limit things such as non virtual copies that get lost, filed wrong, destroyed etc. There may be a better way, I really don't know. I do know that it allows us to edit individual fields and it is simple enough that even I can create a form haha.
I was at the dr office today for my kickass daughters 4mo checkup and I noticed they were using the Motions. I've been considering iPads and similar, however battery life is an issue for all devices regardless so, interchangeability is a must. I talked to three different people and they all have had really success with the 2 models they have in house. Only complaint was battery life of about 2-3 hours which is fine in my book. If an inspector only needs to swap out once when they come in and mid shift then I can justify that need.
Here's my needs. I have a roving inspector which is a new position I am trying to make successful. This job consists of walking throughout the facility with basically a tool cart work station. Ideally in my head a paperless inspection would make life easier to deal with plus give us another form of document control which again is highly regulated by the FDA specifically meaning I need traceability. I can scan employees badges as identifiers as to whom did what and when(electronic signature) for accountability. Plus it helps us with trending. They will be conducting in process inspections on material finish, measurements, materials, ink test(anodize) etc...I'm trying to bring out facility into a new realm of technology. I think improvements like this will cost the initial coin but over a years time pay for itself(minus licensing) 10fold.
I realize the above was poorly written haha It's all over the place

Edit: go Boston