I am running the following code and giving me this error : FPDF error: This document (testcopy.pdf) probably uses a compression technique which is not supported by the
Here is my answer from another topic:
"It can be overcome by re-saving the template and change compression type. In Adobe Acrobat Pro go to File->Save As->Optimised PDF-> Popup left list - Clean Up, Object Compression Options -> Change to "Compress document structure" -> OK to save"
Ref. Editing password protected pdfs with fpdi