You can compare any two versions of a drawing – or two separate documents – and see exactly what changed. Differences are highlighted directly on the drawing, either overlaid on a single view with color highlighting or side by side with synchronized zoom.

You can compare flat formats (PDF, TIFF) and the CAD formats supported by the Autodesk Viewer, including DWG.

Notes:
– This feature is available in environments where the Advanced Viewer or the Autodesk Viewer is activated. To compare CAD files, the Autodesk Viewer integration must be activated on your tenant. Contact your AODocs sales representative for activation.
– To compare attached Word files, use the Compare feature in attached Word files instead.

This article explains how to:

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Which files can you compare?

You can compare two files of the same format family:

Note: You can't compare files of different formats – for example, a PDF with a DWG. When you select the second file, only files of the same format family are available.

Start a comparison

1. Open an attached file in the file preview.

2. Select Compare files in the toolbar. The button is available when the open file is in a comparable format.

3. In the Compare versions dialog, define the two files to compare. All fields are required for both columns:

• Reference version – the baseline for the comparison.
• Compared version – the file to compare against the reference.

For each column, select:

• the document – your current document is pre-selected; you can search for any other document in the library
• the version – by default, the latest version as reference and the previous version as compared
• the attached file – only files of the comparable format are listed

4. Click Start comparison. The comparison view opens.

Tip: To compare the two latest versions of the current document, you don't need to change anything in the dialog – just click Start comparison.

Review the changes

Overlay mode

In Overlay mode, both files are superimposed and the differences are color-coded:

You can show or hide the Added, Removed, and Unchanged content independently to focus on specific changes.

screen: Overlay mode on a PDF drawing, with red and green highlighted differences and the Added / Removed / Unchanged filters visible.

For PDF and TIFF files, open Settings & Filters to fine-tune the comparison with the Contrast sliders:

• Tolerance – how sensitive the comparison is. Increase the tolerance to ignore minor differences such as scan noise.
• Opacity – the intensity of the color highlighting over the drawing.

Note: For TIFF files, all differences are highlighted in red – without the added/removed distinction.

Side by side mode

In Side by side mode, both versions are displayed next to each other. Panning and zooming are synchronized, so you always look at the same area of both files.

Other tools

• Use the swap button to reverse the reference and compared versions.
• For CAD files, use the Autodesk change navigation tools to filter and step through the added, removed, and modified elements.
• Use Back to return to the file preview.

Save or download the comparison

For PDF and TIFF comparisons, you can keep the result. In the comparison viewer, switch to Overlay mode (Save file as isn't available in Side by side mode), select Save file as, then:

• Download – save the comparison as a PDF on your computer.
• Save as new attached file – attach the comparison as a new PDF file on the document. The default file name is the document title followed by (diff); you can edit it before saving.

screen: The Save file as menu in the comparison viewer, showing the Download and Save as new attached file options.

Notes:
– The saved file is a snapshot of the current overlay view, with your tolerance, opacity, and filter settings applied.
– CAD comparisons can't be saved or downloaded – they're available only in the comparison viewer.

Limitations

• For PDF files, only the first page is compared.
• The comparison of PDF and TIFF files is visual: differences in scanning quality or alignment can appear as changes. Increase the Tolerance to reduce this noise.
• You can't compare files of different formats.
• CAD files must be ready in the Autodesk Viewer before they can be compared. If the file is still being prepared, wait for the conversion to finish and try again.
• Annotations aren't available in the comparison view.
• Word and other office files aren't handled by this feature – use the Compare feature in attached Word files.

Troubleshooting

I don't see the Compare files button. The open file isn't in a comparable format (PDF, TIFF, or a CAD format supported by the Autodesk Viewer), or the required viewer isn't activated on your tenant.

I can't compare my DWG file. The file may still be in preparation for the Autodesk Viewer – this can take from minutes to hours depending on its size. If the drawing uses external references (XREFs), run Verify external references on the file first, and add any missing referenced files to the document.

Everything is highlighted as changed. The two files are probably scans or have a slight offset. Increase the Tolerance in Settings & Filters to ignore minor differences.

Related articles

• Use the Compare feature in attached Word files to compare versions
• Preview attached files
• Manage document versions in AODocs libraries