Multithreaded PDF Printing to same printer causing garbled characters

I have a windows service that runs several (5 at the moment) concurrent processes to print PDF documents using PDFTron.
I have the service initializing PDFNet at the service start.
Then each individual thread will run, grab print jobs from a database, then call StartPrintJob on the file path. Each file is different.

However, I’m finding that if I print several different documents in parallel to the SAME printer, one will come out garbled. If I print them one at a time, they all print fine.

Is there anything specific that needs to be done in code the ensure that printing several documents in parallel to the same printer are thread-safe?

This should work fine.

Can you post one of the garbled files. If you can’t here, please send it to support at