<p>There doesn't appear to be any Perl libraries that can open, manipulate, and re-save PDF documents that use the newer PDF version (1.5 and above I believe) that use a cross-reference stream rather than table.  Does anyone know of any unix/linux-based utilities to convert a PDF to an older version?  Or perhaps there's a Perl module in CPAN I missed that can handle this?</p>

I would try running it through ghostscript with appropriate parameters.
Something like
```
gs -dBATCH -dNOPAUSE -sDEVICE=pdfwriter -dCompatibilityLevel=1.2
```