Snap to Edges: Measure PDF Content Precisely Without a Steady Hand

Clicking an edge to the nearest pixel is fiddly, and a 0.3 mm error matters when you are checking a margin. Snap fixes that by pulling your cursor to the nearest edge of the content.

What snap does

With the magnet button on (it is on by default), PdfRuler looks within a few pixels of the cursor for a sharp change in brightness on the rendered page: the edge of a box, a line, a letter, an image or the page border. If it finds one, the cursor locks to it and a ring appears. This works on each axis separately, so you can snap to a vertical edge while sliding freely along it.

What snaps

• The crosshair and the X/Y readout.
• Placed points and the dotted preview line.
• Guides you drag from the rulers (not when you drop one off the page to delete it).
• Points you drag around afterwards.

Get finer results

Snap works from the rendered pixels, so precision follows zoom. At 100% an edge is found to about 0.25 mm; zoom to 400% and it is far finer. See zooming without losing accuracy.

Turn it off when you need to

• Hold Alt to bypass snap for one click.
• Click the magnet to turn it off completely; the setting is remembered.

Snap needs a PDF open and, because it reads pixels, works on any content without parsing the file. For exact vector sizes use Auto-measure instead.

Frequently asked questions