Hi Vini,
Thanks for a great plugin!
I have been creating a lengthy PDF and it was working perfectly until the very end, but just now I started receiving this error: 
I tried removing the elements which might have caused it and tried again with the set of elements that I am 100% sure I saw working before, but the error continues to pop up.
Interestingly, the PDF is still created and stored in the DB (although a lot slower). Any idea how to fix this?