When setting dimensions in Page Designer, you must specify lengths in pixels, not inches or centimeters. This makes things tricky when you know the size you want in inches in or centimeters.
Per this support page, Page Designer uses 109 pixels per inch. That means if you want a box 1" by 1", the height and width should be 109 pixels by 109 pixels.
Unfortunately, 109 is a prime number, so if you want partial inches, you will need to do some rounding.
- use 55 pixels for half an inch (really 54.5)
- use 27 pixels for a quarter inch (27.25)
An 8.5x11 piece of paper (letter size) would be 926.5 pixels by 1199 pixels.
If you are outside of the US, A4 paper is 210x297mm. And 109 pixels per inch is about 43 pixels per centimeter, but all the rounding makes things mucky. It is better to convert pixels to inches and use 8.25x11.75 inches as the dimensions of A4 paper, yielding 899 x 1281 pixels.
Why 109 pixels per inch? It’s all about monitors. For print 300 dpi (dots per inch) is very common. And 72 or 96 pixels per inch used to be very common for computer displays. But computer monitors became capable of displaying higher resolutions and different aspect ratios, so different monitors show a different number of pixels per inch.
If you have 49" monitor with a 32:9 aspect ratio and 5120×1440 resolution, you should see 109 pixels per inch, and Page Designer sizes on the screen will match what is printed. Or you may have some other combination that makes 109 pixels per inch. But your monitor may very well have a different PPI, so don’t worry if 1" (109pixels) printed from Page Designer doesn’t look like 1" on your display.