Docutils has the raw
directive for passing data through to the final output untouched. In the documentation they demonstrate this for the LaTeX and HTML outputs. rst2pdf seems to support this directive: in the manual they use the raw directive to include some text/commands in the final PDF (see the section headed Raw Directive) but they do not demonstrate using this directive for including external PDF files.
If rst2pdf does support this feature, you should just be able to use:
.. raw:: pdf
:file: your_pdf_file.pdf
:encoding: the encoding of the PDF file, if different from the
reStructuredText document's encoding.
I have just had a go at doing this (if in doubt, give it a go) and I get a number of UnicodeDecodeError
s, so the feature seems to be supported but I can't get it to work.