I am making an invitation in PS, (honestly because I know it so much better than ID), which will eventually be printed. I set the canvas and image size to be 5x7, but it is so much larger than that. Resolution is 150px/inch and the width is 750 px and height is 1050px. The inches on my rulers are ridiculously large and not accurate. Is this some sort of simple problem or a PS bug? I'm using CS5.
If you were sending this to a printing press, it would need to be 300dpi (dpi = dots per inch or ppi=pixels per inch)... and CYMK
(which is why Indesign or Illustrator are traditionally used for layout)
If your document is 5 x 7... multiply 5 x 300 = 1500 and 7 x 300 = 2100...
Hence your pixel size would 1500 x 2100.
For desktop printing, 150dpi should be okay, but 200 dpi wouldn't be a bad idea. BUT for text heavy items, 300 dpi would improve legibility.