State your OS and OS version: MacOS 13.6.3

$ pdfcpu version
pdfcpu: v0.8.0 dev

$ pdfcpu validate ./pkg/file_executor/test.pdf
validating(mode=relaxed) ./pkg/file_executor/test.pdf ...
validation error (obj#:296): dict=annotDict required entry=Subtype missing

I will post my pdf to your email with this issue link