I know that Adobe Acrobat Reader DC can select the Microsoft Print to PDF printer to output to a PDF file with Print As Image checked in the Advanced Print Setup dialog. However, I want to use a command to do this. I tried the following command, as a result it failed to convert each page to images (Note the output file is still PDF).
gs -o 0.999.watermask.compact.screen.pdf -sDEVICE=pdfwrite -dDetectDuplicateImages=true -dPDFSETTINGS=/screen 0.999.watermask.pdf
References
Your -switches include -dDetectDuplicateImages=true
which under the circumstances should be superfluous and the device selection can be from one of four as pointed out by KenS.
gs -o 0.999.watermask.compact.screen.pdf -sDEVICE=pdfimage32 -dPDFSETTINGS=/screen 0.999.watermask.pdf
If you want to emulate MS Print As Image PDF on Windows you would find the result in some ways inferior (and often many times bigger). But for comparison it would be,
NOTE:- "%%printer%%... is for a batch file for a command line use "%printer%...
gswin64c.exe -sDEVICE=mswinpr2 -dNoCancel -o "%%printer%%Microsoft Print to PDF" -dPDFSETTINGS=/screen -f "0.999.watermask.pdf"