Force CUPS print server to fit-to-page if job is not A4

Question

I've setup a CUPS print server on Debian Stretch and I need a way to modify print jobs that don't use A4 page size.

I have clients (iOS) that cannot set the paper size and will send for example a PDF that is in letter size to the print server which will send it to the printer and the job will fail because the paper size is not correct.

The printer is configured with A4 paper.

I'm using the Generic PostScript driver on the cups server and I've set the default page size to A4.

I've also tried to modify /etc/papersize to A4 but that makes no difference.

I've tried lpoptions -p myprinter -o fit-to-page but it has no effect. Also tried lpadmin -p myprinter -o fit-to-page but it has no effect.

I've enabled debugging and can see the following filters are used:

pdftopdf (application/pdf to application/vnd.cups-pdf, cost 66)
pdftops (application/vnd.cups-pdf to application/vnd.cups-postscript, cost 100)
- (application/vnd.cups-postscript to printer/myprinter, cost 0)

If the print job is sent in A4 then everything is fine.

How I can get the cups print server to check if the page size is not A4 and if so fit the content, e.g. letter PDF to A4?

Do I have to write a custom cups filter or is there some other way?

Answer 1

The server is only setting the default page size, if the client sends the job as another page size then it will process it with that page size. If it isn't already set, you should set the default on the clients as well. Although user may also change the page size and it's also possible the software submitting the job may present the user with a different default based on the size of the document being submitted.