What is the maximum number of simultaneously open PDF files in PDFNet SDK?

Q: We have a workload which needs to have around 5000 PDF documents
in memory *at the same time*.

After approximately 2100 PDFDoc objects have been instantiated PDFNet
throws an exception [1], stating that no more temp files could be

The temp folder (%TEMP%) indeed contains ~2100 files named Trn[1-4 hex

Now if we disable PDFNet Caching
(pdftron.PDF.PDFNet.SetDefaultDiskCachingEnabled(false)) then it works
fine. But we can’t do that in some cases with limited RAM.

So could you please fix the temp file generator to not error out after
~2100 files?

pdftron.Common.PDFNetException: Exception:
                 Message: An error occurred during page import: Could
not open a temporary file. Make sure to close unused documents.

A: The maximum number of PDF files that can be simultaneously opened
in a single process is 2048.
This a hard upper limit for the number of simultaneously open files
accessed through the C run-time library (CRT). For more info, please


Besides SetDefaultDiskCachingEnabled() you could limit the number of
simultaneously opened files to ~2K (e.g. have a cache of documents -
it is very unlikely that all of them need to be used at the same
time), or have multiple simultaneous processes.