How to change the scale of measurement for PDFs in Foxit PhantomPDF and Foxit Reader

by Scott Nguyen, Integrated Sales and Support


Using the Measure Tools, Foxit PhantomPDF and Foxit Reader make it easy to measure distances and areas of objects in PDF documents. That’s useful when you’re creating manuals, instructional guides, and computer-aided design (CAD) drawings. We covered how to do so in this post.

Some users who rely on measurement accuracy have told us that they sometimes receive a PDF drawing in which the scale is off from what the image states in the document. That can happen for reasons such user error, or when drawings aren’t directly exported from an Auto CAD program. This can be a big problem in any setting where precise measurements are critical.

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If this happens, you may need to customize the scale in order for your PDF file to accurately reflect the measurements in use. To do so, you need to select File Preferences Measuring and use the Use Scale and Units From Document (When present) option. Then all the following measurements will use the embedded scale ratio you set.

To calibrate the scale ratio for your document for an accurate result, you can choose either of the following methods:

  • With the Use Scale and Units From Document (When present) option selected:
    1. Click Calibrate in the Scale Ratio group and then click the two points of the line whose actual length has already been known. (Tips: When drawing, you can hold down SHIFT to snap the two points horizontally, vertically, or diagonally. You can also click Snap to Paths in the Snap group to capture the path in the page.)
    2. When the second point is selected, the Calibration dialog box pops up.
    3. Type the actual length that the line represents and choose the appropriate unit, which will set a new scale ratio.
    4. Then in the Scale Ratio group or the pop-up Calibration dialog box, click Store Scale in Page to apply the new scale ratio to the current page, or click Apply to All Pages to apply it to all pages. The new scale ratio will be embedded into the page or all pages respectively, replacing the original embedded scale ratio.
    5. As the scale ratio is embedded into the document, the measurements in the document change accordingly.
  • With the Use Scale and Units From Document (When present) option unselected, define a custom scale ratio in the Scale Ratio group, or click Calibrate in the Scale Ratio group to define a new scale ratio. The defined scale ratio will only be applied to the current page.

If you want to see the current measuring result, including real distance, angle, horizontal and vertical position, etc., check Show result information.

Now, you can get customize the measurements that you need to ensure that content in your PDF documents reflects the scale being shown in any image or diagram.

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