I actually have been living with this for awhile but realized that it is just getting unbearably slower over time. It takes approximately 30s to generate any PDFs for any documents including Sales Orders, Invoices etc. I run ERPNext on Ubuntu and based on a simple version check have wkhtmltopdf 0.12.2.1 (with patched qt).
demo.erpnext.com generated PDFs in 1 or 2 seconds. Anyone encountered similar problems?