In addition to xdg's excellent pointers, you might also want to look at my article on the subject.

As for what's needed in this specific area, the biggest thing lacking is tests. When I took over PDF::Template 4 years ago, there was no easy way of testing PDFs. One of the reasons I was so interested in converting PDF::Template to use PDF::Writer as its engine is that writing tests for PDF::Template become much simpler (see how I wrote tests for Excel::Template as a good example). In the meantime, Test::PDF has been released to CPAN and would make a very good way to test PDF::Template or PDF::Writer.

The most immediate need is to get off of the PDFlib v3 API and either onto PDF::Writer (best solution) or the PDFlib v6 API (better than nothing). After that, there's a number of directions you can go.

• Build in support for HTML-like tables. (The single-most requested feature).
• Move off of the XML templating format and to a TT-based format. (Fixes a bunch of design flaws and gets us out of the templating business and into the PDF-generation business)
• Make a bigger deal of the custom nodes feature.
• Add the ability to draw (second-most requested feature)

As you have low-level PDF experience, this sounds like it might be a good fit. I'll /msg you my email and we can chat further.