What could be the the best Open Source alternative to Adobe Acrobat?

[Itachi5CEE]

What could be the the best Open Source alternative to Adobe Acrobat (The basic Free version, ofcourse)? I've been the KDE Okular and it's been working like butter. Only problem I face is verifying signatures on PDFs. Any recommendations for a better alternative?

[Bevi Chagnon - PubCom.com]

There isn't one that I can recommend.

None of the others meet the PDF standards, neither the core ISO 32000 standard or subset standards for accessibility, archiving, engineering, print and graphic arts, etc.

I know several of the competing PDF products and I can say that all of them take an Adobe Acrobat document, reverse engineer it, and develop their program based on what they discover.

Adobe developed the concept of digital signatures in PDFs. How well do you think the others are going to do on this task?  Maybe in time they'll create better PDF software, but for now they're more like knock-offs, in my opinion.

A knock-off Rolex watch? I'm ok with that.

Knock-off digital signature software for a legal document? No. I don't think so!