It sounds like your include or linker path isn't set correctly. Strangely enough, either A) include or B) linker path not finding the libpd source causes the same error on many compilers.
As next steps, I recommend investigating what your include path is usually set with the capital "i" switch for your compiler: -I If that includes /path/to/libpd/include or similar, then its probably the linker path.
The linker search path can be checked by looking at the -L (capital L) switch to the compiler. This should point to where the .a or .so of libpd is.
Hope that helps! -Harry