wkhtmltopdf is by far the best tool available to make PDFs. Yes. I have tried ReportLab and PISA. ReportLab might be more powerful but what you gain in fine-grained control you lose in hours and hours of productivity.
Anyway, I've learned something about font-size shrinkage and using wkhtmltopdf.
Basically, if use percentage to change a font size (Arial in this case) you get a PDF where the letters are unevenly spaced between. It took me a while to figure out what the hell was going on until I changed the font-size from
90% to exactly
('font-size:90%'; the spots of red are my highlights of the ugly spacings)
('font-size:11px'; not perfect but much better)
So, at first I thought this was the first time wkhtmltopdf has disappointed me but I guess I'll just have to remember not to use percentages and continue to favor wkhtmltopdf as my choice of weapon in the PDF production world.