How can I change the DPI/size of a PDF or create it at that?

[Wuktrio]

I have a PNG measuring 6000x4500 pixels and I want to print it at 300 DPI so that would make it exactly 20" x 15".

When I create a PDF out of it there's no option to change the DPI value, it's always 72, which creates the PDF at 83.33" x 62.50".

Is there a way to either create it at 300 DPI from the start or resize it to 20" x 15"?

Thank you!

[Test Screen Name]

With Acrobat it uses only the resolution (ppi) in the file itself. To make it another size you need to use another app. Photoshop if you have it.

[Wuktrio]

Thank you, that worked, but I didn't know images had a PPI value.

[JR Boulay]

"I didn't know images had a PPI value."

You can continue to ignore it: Image resolution is an outdated concept inherited from paper photos and scanners of the 20th century.

See: https://translate.google.fr/translate?sl=fr&tl=en&u=https%3A%2F%2Fwww.abracadabrapdf.net%2Fressource...

[Dov Isaacs]

To properly prepare a PDF file of a raster image and get the size, resolution, and color space correct, you would be best off to open the image in Photoshop or equivalent and perform the resizing in that software, saving the results as a PDF file.

[Wuktrio]

Thank you, but now I have another question:

I thought PPI was not a value for images? Isn't PPI only for printing if you know which dimensions you want to print the image in?

[Dov Isaacs]

Resolution (PPI) is effectively metadata that accompanies many if not most images. It is useful to determine what is the actual size that the image will either print at or place at (such as in InDesign, Illustrator, or even Word) without further manipulation either at print time or when placing the content.

[JR Boulay]

The size of the PDF don't matter, you just have to scale it to 20x15 when printing.

[Wuktrio]

I know, I can simply print it at 24% to make it exactly 20x15, but I wanted to know if it's possible to change that so I can print at 100%.