If your PDFKit and wkhtmltopdf is working on your development server, probably in OSX, but not working on your production server, which is probably running linux, it’s because you’re missing X Server.
There are a few ways around this, some emulate X Server, but that seems hacky. I read through the wkhtmltopdf docs and read that a patched qt framework will allow you to use wkhtmltopdf without using X Server.
Here’s what I did on my Ubuntu Box to get this to work (note: the compile time for qt was almost 2 hours, and you’ll also need to have git installed):
sudo apt-get build-dep libqt4-gui libqt4-network libqt4-webkit
sudo apt-get install openssl build-essential xorg git-core git-doc libssl-dev
git clone git://gitorious.org/+wkhtml2pdf/qt/wkhtmltopdf-qt.git wkhtmltopdf-qt
./configure -nomake tools,examples,demos,docs,translations -opensource -prefix ../wkqt
Next install wkhtmltopdf:
git clone git://github.com/antialize/wkhtmltopdf.git wkhtmltopdf
Run ‘wkhtmltopdf’ in shell and you should see it load correctly instead of seeing the x server error. Running ‘wkhtmltopdf-proxy’ should do the same, which is what PDFKit uses.