PDFtk for HP-UX 11.31 Itanium 64

Hi Unix and HP-US experts,

I have a need to encrypt/give password to PDF files in HP-UX servers, but unfortunately I am new to unix and hp-ux.

My server is HP-UX 11.31 running on Itanium 64 bit architecture. I have downloaded and installed PDFtk from this link:
hpux*connect*org*uk/hppd/hpux/Text/pdftk-2.02/ --> I chose 11.31 Itanium 2.0

I have also installed the libgcc from here:
hpux*connect*org*uk/hppd/hpux/Gnu/libgcc-4.2.3/ --> I chose 11.31 Itanium 2.0

But when invoking any pdftk command, I got the following error:
[HP ARIES32]: Core file for 32-bit PA-RISC application
[HP ARIES32]: /usr/local/bin/pdftk saved to /core.pdftk

This looks like the OS somehow cannot run the bin with help of HP aries.

Does anyone ever encountered this kind of error? Mind sharing the solution or maybe guiding me to solve it?
Or maybe if there is a way to compile the tool directly on ia64 machine, that would be good.

I am also open for suggestion of other pdf encryption tools that can run on HP-UX 11.31 ia64.

Thanks!

Ghostscript will create password protected pdf files.
Ghostscript, Ghostview and GSview