Hi,
Once you are using the free version, can you please ask your questions on https://wordpress.org/support/plugin/file-renaming-on-upload ?
Regarding your question, I don’t think this error is related to File Renaming plugin but to your TCPDI library, which is a tool that imports / generates pdf files. Can you please check if your TCPDI tool is working fine?
I tested a downloadable file with the renaming plugin and it’s working just fine