You say HPUX 11, but running on what?

There are basically five different runtimes, as follows....

CPU width Packaging
PA-RISC1.1, 32 bit mode, SOM
PA-RISC2.0, 32 bit mode, SOM
PA-RISC2.0, 64 bit mode, ELF
Itanium-2, 32 bit mode, ELF
Itanium-2, 64 bit mode, ELF

The immediate giveaway is if the library is of the form

"lib*.so[.major[.minor]]"

then it's ELF, if it's

"lib*.sl" or "lib*.major[.minor]"

then it's PA-RISC, if it's 32 bit then it's SOM.

You can only link like with like.