I would like to measure the size of the margins and other distances in a PDF without having to print it out. I would like the results in "as printed" units (e.g. inches or cm once printed)

Is it possible to measure PDF margins or other distances with Preview?

If not is there another (hopefully free) application that can?

Update: I see at this TeX stack exchange post some options for windoze and linux. Any thing like this for OSX?

2 Answers 2


Found it!

In Preview,

  1. open the Inspector (Command-I)
  2. Select the Crop and Rotate tab, whose icon looks like a small ruler. Change the units as required
  3. Now use the select area tool and the corresponding (printed) dimensions will be shown in the Inspector.

As an alternative, you can also download Free Ruler, which displays a nice ruler on screen, though requires care in both setting the ruler DPI and ensuring that the PDF is viewed at 100% size.

  • 2
    No longer exists in OSX 10.13.6 Commented Sep 15, 2018 at 15:46
  • 2
    Just checked and it works in Mac OS 10.13.6.
    – seren
    Commented Oct 10, 2018 at 23:29
  • @seren - can you elaborate? The "Crop and Rotate tab, whose icon looks like a small ruler" isn't visible on the Inspector for me. I'm only seeing 4 tabs.
    – cathalog
    Commented Dec 4, 2018 at 14:34
  • 1
    Could you be viewing an image rather than a PDF? When viewing a PDF, I see 5 tabs, including the "Crop" ruler icon, but I did notice that the Crop icon disappears when viewing an image. I'm running Preview 10.0 (944.5).
    – seren
    Commented Dec 4, 2018 at 18:40
  • 1
    As of macos 13.4, when a PDF is open the crop tab in the inspector window is still there - but its icon is not a ruler, but the standard "crop symbol" that is used in lots of image editing programs.
    – hmijail
    Commented Jul 19, 2023 at 23:23

In macOS Mojave, this works:

  • Tools > Show Inspector (Command-I)
  • Click the 'ruler' tab in the inspector window, and select the units that you want
  • Tools > Rectangular selection
  • Drag in the pdf to make a selection, and the inspector will show the size of your selection

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