PPC PDF viewers

I've heard that a few PDF viewing softwares that were designed for PPC work with HPC 2000. Some examples are PocketXpdf and Acrobat Reader for PocketPC. I tried with Xpdf, but after the install, it was not a valid CE application. How do I make these types of softwares work with the HPC 2000 platform. Also, technologically, how come HPC 2000 is capable of running PPC apps when other CE operating systems can't?

Not sure what you mean by "other CE operating systems can't." Plenty of Pocket PC apps will work on CE 4.x .net, CE 5, and CE 6 devices. Usually they need DLL files compiled for Pocket PCs, though. Adobe Reader, for example, needs the Pocket PC version of mfcce300.dll, as well as its dependencies (aygshell.dll and doclist.dll). Not only that, but many apps written for Pocket PCs can even work on H/PC Pro devices (primarily Visual Basic apps), and some even work on CE 2.0 devices (.NET Compact Framework 1.0 apps). Which version of PocketXpdf are you using? It may be a version for Windows Mobile 2003, which is based on CE 4.2 .net. There are tons of threads on these forums talking about making Pocket PC apps work on H/PCs and core CE devices.

The source code is available for xpdf, and I'm in the process of converting it for my J720. The parser for command line args will need to be looked at again. But, so far I have successfully built the supporting goo.dll.

Sorry, I'm sort of a noob. I don't do programing, I just collect vintage electronics. Anyway, are there any free pdf viewers that work with a MIPS processor on HPC 2000?

Adobe Reader 1.0 for Pocket PC will work:

http://www.hpcfactor.com/support/cesd/s/0067.asp

Do a web search for "ANSYR Primer 2.3" or "ANSYR Primer 3.2" which is the newer version. They both had trial versions with builds for HPC2000 MIPS devices. The became non-functional after 30 days.