How to Compare Documents in Bluebeam Revu (2026)
Compare two PDFs in Bluebeam Revu with Compare Documents or Overlay Pages: the steps, the alignment and sensitivity settings, and when each tool fits.
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To compare documents in Bluebeam Revu, go to Document > Compare Documents, set the original drawing as Document A and the revision as Document B, choose an alignment and select OK. Revu creates a new PDF ending in "_Diff" with the differences marked as orange cloud markups. If you want the two files shown in separate colors instead, use Document > Overlay Pages.
This guide covers both tools in Revu 21, what changes in Revu 20, the settings that decide whether a comparison finds the right differences, and how the same job works in Notch, which is our product. Bluebeam steps come from its support site, checked October 29, 2026.
What are the ways to compare documents in Bluebeam?
Revu has two tools for comparing drawing revisions. Per Bluebeam's comparison of the two, both create a new PDF and leave the original and the revision unchanged.
| Compare Documents | Overlay Pages | |
|---|---|---|
| Menu | Document > Compare Documents | Document > Overlay Pages |
| Output | New PDF ending "_Diff", differences as cloud markups | New PDF with each file on its own colored layer |
| Differences listed in the Markups List | Yes | No |
| Compare more than two PDFs | No | Yes |
| Plan (Revu 21) | Core, Complete or Max | Bluebeam does not state a requirement |
| Works with scanned PDFs | Yes | Not marked in Bluebeam's table |
Pick Compare Documents when you want a list of changes you can sort, track and report, or when the PDFs are scanned. Pick Overlay Pages when you want to read the changes in context, or compare more than two issues of a sheet. Overlays are easier to read when both pages are at the same scale, so calibrating the scale first helps.
How do you use Compare Documents in Revu 21?
Open both PDFs, then follow these steps from Bluebeam's support article.
- Go to Document > Compare Documents.
- Set Document A and Document B. Bluebeam says Document A should be the original drawing and Document B the revised version.
- Choose a Page Range for each document: All Pages, Current or Custom, for example 1-3, 5, 9.
- Choose an Alignment method (see the table below).
- Choose an output folder in the Output section.
- Optional: select Split-screen view or Turn on Dimmer. The dimmer makes the differences easier to spot.
- Optional: select Advanced Options to change how the cloud markups look and how sensitive the comparison is.
- Select OK.
Revu writes the "_Diff" file and lists each marked difference in the Markups List, where you can sort, filter and check them off like any other markup.
Which alignment should you choose?
| Alignment | Use it when | Notes from Bluebeam |
|---|---|---|
| Page Align (default) | Minor revisions, same scale and position on the page | Recommended for drawings that are otherwise the same |
| Auto Align | Drawings of different sizes or scales | Finds the points of alignment between the PDFs automatically |
| Manual Align | Auto Align does not line the pages up | Pick three matching points, in the same order, on each drawing |
| Select Window | You only care about one region | Draw the area to compare |
For Manual Align, turn on View > Snap to Content so the points land on the line work.
How do you use Overlay Pages in Revu 21?
- Go to Document > Overlay Pages.
- Add the other files with Add Files or Add Open Files. To remove one, select it and choose Delete layer.
- Optional: select Edit Layer > Select Region to overlay only part of a page.
- Choose Page Align, Auto Align or Manual Align.
- Select OK.
Each layer gets a color automatically, and Bluebeam recommends keeping the defaults. Revu saves the result as a new file so your originals stay as they were.
Can you use both tools on the same revision?
Yes. Bluebeam describes a Compare + Overlay workflow that puts the cloud markups on top of the overlay.
- Run Document > Compare Documents with the original as Document A and the revision as Document B, then select OK.
- In the comparison PDF, go to Markups List > Markups > Export Markups and save the file.
- Save the comparison PDF with File > Save As, then close it.
- Run Document > Overlay Pages with the same two PDFs and select OK.
- In the overlay PDF, go to Markups List > Markups > Import and select the exported file.
Bluebeam notes this workflow does not work well with scanned (raster-based) PDFs, and it requires a Core, Complete or Max plan, the same as Compare Documents.
What changes in Revu 20?
The same two tools exist in Revu 20 with different dialogs. Per Bluebeam's article:
- Compare Documents uses an Output Folder selection, and the split-screen view and comparison type sit under Other Options. For misaligned scanned PDFs, use Select Window or Pick Points.
- Overlay Pages adds files with Add. To align, select Align Points, pick three points on the first drawing and the same three, in the same order, on each later drawing, and press Esc to cancel. The result is a new file named "Overlay".
Which Compare Documents settings change the result?
Bluebeam's Advanced Comparison Options page recommends the provided settings and says to change them only if the comparison does not detect differences. Revu includes three configurations: Printed Documents (same printer), Printed Documents (different printer) and Scanned Documents. You can edit one or create a custom configuration, and Restore Defaults resets the included types.
| Setting | What it controls |
|---|---|
| Grid Size | The size of each region that is compared |
| Pixel Density | The difference threshold within a grid area |
| Color Sensitivity | The pixel-difference threshold; lower values detect fewer differences |
| Pixel Proximity Allowance | Checks adjoining areas for similar pixels, and works with Color Sensitivity |
| DPI | The resolution the pages are rasterized at; the default is 72 and 144 gives finer results |
| Margin | Ignores regions around the page borders |
| Include Markups | Renders existing markups, which are ignored by default |
| Include Flattened Markups | Includes markups flattened as "recoverable", ignored by default |
| Subject | Names the difference markups so you can group them in the Markups List |
The Subject setting is useful across issues. If you name it "Rev 3 vs Rev 2", you can sort the Markups List by Subject later and see the history of changes on a sheet. The other markup options, Color, Fill Color, Opacity, Width, Cloud and Locked, change how the difference markups look and whether they can be moved.
Why does the Bluebeam comparison miss changes or mark everything?
| Problem | Likely cause | What to try |
|---|---|---|
| Clouds all over the page | The two pages are not aligned | Switch from Page Align to Auto Align, or use Manual Align with three points |
| Real changes not marked | Sensitivity too low for the PDFs | Raise Color Sensitivity or DPI in Advanced Options |
| Noise on scanned pages | Scan skew and speckle read as changes | Use the Scanned Documents configuration and align the pages first |
| A change inside a markup is missed | Existing markups are ignored by default | Turn on Include Markups |
| Only part of the sheet needs checking | The whole page was compared | Use Select Window |
| Compare Documents is not in the menu | Plan or version | Compare Documents (Revu 21) needs Core, Complete or Max |
How do you compare documents in Notch?
Notch compares with overlays, which behave like Overlay Pages in Revu. Open the current page, add the earlier version from the Overlays panel and align it. Overlays are part of the Notch Solo and Pro plans, and you can try either free for 14 days, according to the plans and billing docs. Pricing changes, so check Notch pricing.
- Open the PDF with the current revision and switch the right sidebar to the Overlays panel.
- Select Add overlay and pick the source: any page from the same document or from another document in your workspace.
- Align it. Drag to move, use the corner handles to scale and the ring to rotate, or use Align overlay… under Fit in Properties to pick two points on the overlay and where each should land. Use Crop to trim the overlay to a title block or one detail.
- Read the color. Color with nothing under it is work that is in the overlay only. Original lines with no tint are work that is on the page below only.
To read it the way Bluebeam shows it, tint the Base drawing too. It is the first row of the page's overlay list. Pick green for the base and red for the overlay, and lines both pages share come out dark. Red then means "only in the overlay" and green means "only in the base".
You can add several overlays to one page, each with its own tint. On the iPhone, iPad and Mac apps, select two documents in the library and choose Compare. Notch does not produce a list of differences the way Compare Documents does, so you cloud the changes yourself on top of the overlay, as covered in how to add revision clouds to a PDF. The compare revisions docs cover each control, and the revision compare page shows what else Notch does around it. For the wider picture of the three tools, see how to compare two PDF drawings.
Frequently asked questions
Where is Compare Documents in Bluebeam Revu?
In Revu 21 it is under Document > Compare Documents. Set Document A to the original and Document B to the revision, choose an alignment and select OK. Bluebeam says it requires a Core, Complete or Max plan. Revu 20 uses a slightly different dialog with an Output Folder selection.
What is the difference between Compare Documents and Overlay Pages?
Compare Documents marks the differences between two PDFs with cloud markups and lists them in the Markups List. Overlay Pages puts each file on its own colored layer and can merge two or more files. Bluebeam's comparison table marks scanned PDFs as supported by Compare Documents and comparing more than two PDFs as supported by Overlay Pages.
Why is Bluebeam Compare Documents not finding differences?
Bluebeam says to keep the default settings unless differences are missed. If they are, check the alignment first, then try the configuration that matches your files, and raise Color Sensitivity or DPI in Advanced Options. Existing markups are ignored unless Include Markups is on.
Can you compare more than two documents in Bluebeam?
Overlay Pages can, because it merges two or more files into one PDF with a layer per file. Compare Documents takes two documents, Document A and Document B.
Next steps
Run Compare Documents on a sheet where you already know what changed, and check that the clouds match before you trust it on the rest of the set. Once you have the changes, update quantities with how to do a takeoff from a PDF, and if you are weighing Revu on a Mac, see Bluebeam for Mac options. To try the same job without a Revu plan or a Windows machine, open the two revisions in Notch and read the revision compare overlay. If you also take off quantities in Revu, see how to do a takeoff in Bluebeam.