Comment 5 for bug 1564249

See https://bugs.linuxfoundation.org/show_bug.cgi?id=1315 why this cannot work.
And QPDF won't be able to do anything about it, either...
There might even be PDF-capable printers on the market (i.e. where the rasterization is not done by gs / poppler on the host), where the form content will not be printed even without the fit-to-page option.

The PDF format generally does not allow arbitrary transformations (as used by pdftopdf in certain cases) to be applied to the ("interactive") Form content - which is stored separately from the Page content.
The usual solution for printing is that the viewer application (Evince, Google Chrome, ...) converts (hard-codes) any Form content into regular Page content before sending the data to the printing chain. Using lpr skips this (non-trivial) step.