Qpdf.exe Download
Melony Holden
However, in your second batch file, you need to actually run the qpdf.exe program separately for each file. To do this, change the FOR loop to execute the qpdf.exe program on each loop:
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 ...
Navigate to C:\Program Files\qpdf-version_numer\bin and execute qpdf.exe (by double-clicking). Windows 10 throws up a security warning, as it's an unrecognized executable file. You'll need to use the more options link to find the button to run the program. This done, Windows will recognize the file as safe to run and allow other software, including R, to use it.
Note that the changelog is incomplete, as Rtools 3.5 isn't frozen yet at the time of writing (2019-03-01). Even though it's not visible on the page yet, qpdf.exe is included in the bin directory after installation.