Usually qpdf::pdf_combine worked fine for a few PDFs, but when I try to combine 500 PDFs get the error: Too many open files.

I found that this error is related to the fact that qpdf opens the files during the process: https://qpdf.readthedocs.io/en/stable/cli.html. There is also a solution with --keep-files-open=[y|n]. However, I think this is not implemented in the R package.

Could I modify pdf_combine that it works?