If I start a new ps file and the canvas is 500 x 500px at X PPI, will it print at 500 x 500px? X being the variable. It shouldnt matter what the PPI is right?

Avoid confusing terms.

It won't "print at 500 x 500px". It'll "print 500x500 px @ a specified resolution to give an image of dimensions = w x h". The resolution will determine your document size and image quality.

The important factors are your original image size (pixel dimensions) and your target output (website, offset printing or something in between).

Pixels are your ingredients. Document size and resolution determines how you print those ingredients (image size & quality).

Uncheck "Resolution" in the Image Size dialogue and you can set whatever document size you wish.

Print quality will vary drastically though. Good @ 300 dpi. Poor @ 72 dpi.

But I'm guessing the reason for that is because monitors can only output certain resolutions and use DPI instead, so they can't possibly show you a high resolution of 300 pixels per inch.

Monitors don't care about DPI (or image resolution).
They only care about image dimensions measured in pixels since 1 image pixel = 1 screen pixel.
The same image looks the same @ 72 dpi or 300 dpi
See http://www.leannehoad.com.au/temp/dpi_test.htm

But all in all, a size 500 x 500px document, whether it is 72 or 300 PPI, should print out as 500 x 500px right?

500 x 500 px means you've got 250,000 pixels to print. No more, no less (without resampling). Resolution determines how many pixels are crammed into how much space i.e. document size and quality.

500 x 500px will print at different sizes subject to resolution. Low res = big print size, low quality unless it's small enough that it doesn't matter e.g. postage stamp size.
Hi res = smaller print size (more pixels per inch PPI), high quality

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Regards

John Waller

Tyler_Jameson

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