I am trying to check a package that I have built (with vignette) using R CMD check --as-cran [my package] in my windows command prompt. All goes well until I ge
I would try
Sys.which(Sys.getenv("R_QPDF", "qpdf"))
Sys.getenv("PATH")
to establish that R is really not finding the qpdf executable, and see where it is looking. You probably shouldn't need to rebuild everything, just figure out why R is not finding the qpdf executable ... does running qpdf from a terminal window work ... ? How are you starting R, and did it have a chance to get the new PATH definition (i.e. do you need to open a new terminal window, or ?? reboot ??)
The incantation above was extracted from tools::compactPDF, from the default value of the qpdf argument, on a Linux machine. You should check for yourself, in case (e.g.) the Windows version is looking for qpdf.exe rather than qpdf ...