In your print dialog there should be an option to "Print to PDF" (at least on MacOS- and Linux-based systems).

polhallen wrote

I've cups-pdf (linux) but I'd have an option to "save to pdf file"

All CUPS versions I know of (and I know CUPS since it has been invented by EZ-Software in the 1990s long before it was bought by Apple) have such an option to print into a file, even the Linux version does have it.

See https://embraceubuntu.com/2006/03/23/print-to-pdf-using-cups-pdf/

In Common Unix Printing System (CUPS) it is the print dialog's responsibility to direct any output to either the printer, a PDF file or a program, but not the responsibility of a device or a software generating any output.

where can I write wishlist of AC50?

Send a ticket to TP-Link support (address is on your country's website), but I doubt that TP-Link will add a PDF generator to the AC50, since such a generator is already there - in your browser displaying output from AC50.

It's a browser-related problem. If a browser implements its own print dialog there is most often a way to force it to use the system's (Debian) dialog instead. Maybe this works better.