I've decided that there needs to be a feasible, openly free way, to print interesting test pages, so I've decided to start up a Git page that contains just that:

https://github.com/SecularSteve/OpenPrinterTestPages

Name's a bit clunky, but I'm not aiming for authenticity.

The benefits are pretty standard:

-No Watermarks
-No Low-res JPEGs
-No Copyrighted fonts
-No excess Ink-wasting
-Printer Neutral
-CC0-1.0
-It was fun to make

Anyone want to contribute?

I'm planning on releasing the CMYK, RGB, B&W and Stress-test A4 pages as I go on.

Welcome aboard!

Thank you for sharing this, looks like a huge project!

Made many test images in the past, although mostly never specifically meant to produce them onto a printable template.

For example this one was focusing on the luminance levels of saturated colours: https://openclipart.org/detail/235385/hue-blending-test-2

There are quite a few things I'd add into a test template. Unfortunately can't contribute with new material in the near future.

While at it, attaching a test file I used two years ago.

It was used for choosing the "best" possible blue colour of the printer and see which stroke width appears still clean as they get thinner.

My experience lead to abandoning colour printing with cmyk because the "blue" never looks close to a solid fill/spot colour.

And the stroke width below 0,1 mm gets jagged when printing with black only. If the black is overlayed other graphic content, it prints worse.

By the way, the stroke widths from 0,7 and 0,5 mm to 0,18 and 0,125 are supposed to represent the widths used in drafting standards. 

There is also a standard for lettering, which isocpeur and osifont covers to some extent. 

(Another project I worked on, to make an alternative to those which actually fits well with the intended sizes.)

Personal opinion, I wouldn't print texts based on their px sizes and would possibly compare a few fonts for testing legibility.

For instance the mentioned standard font is iso 3098 which is less legible than the older german standard font, 1451 Mittelschrift.

Roboto https://fontlibrary.org/en/font/roboto is a good choice for testing too (and has a good license) and this would be an interesting one as well https://www.type-together.com/lipa-agate-font

-latter needs a free alternative though.   

Interesting suggestion. I'll see if I can fit it in anywhere.

And that's a pretty good way to test line-thinness-outputs (the page). But that's also the intent of the project.

I want everyone to have an accesible way to test their machines.

P.S.
The font I've used here is OpenSans.