The two main ways to scan both sides

Most scanners can handle two-sided documents in one of two ways: either your scanner has an automatic document feeder (ADF) that flips pages for you, or you scan one side, then manually flip the stack and scan the other side. Which method you use depends on what equipment you have and how many pages you're scanning.

If your scanner has an ADF — the tray that pulls pages through automatically — look for a setting called "two-sided," "duplex," or "both sides" in your scanning software. If your scanner is flatbed only (the kind where you place one page at a time on a glass surface), you'll need to scan all pages face-down first, then flip the entire stack and scan again.

Key Takeaways

  • Automatic document feeders (ADF) can scan both sides in one pass if your software has a duplex or two-sided setting enabled.
  • Flatbed-only scanners require you to scan one side completely, then flip the stack and scan the other side as a separate batch.
  • The order matters: if you scan pages 1–10 face-down, then flip and scan, your software needs to know to interleave them correctly (page 1 front, page 1 back, page 2 front, page 2 back).
  • Some scanning software can automatically arrange two-sided scans into the right order; others require you to manually reorder the pages afterward.

Using an automatic document feeder for both sides

If your scanner has an ADF, load your pages into the tray face-up, with the top of the first page pointing toward the feeder. Open your scanning software — this might be the software that came with your scanner, or a program like Windows Fax and Scan on Windows or Image Capture on Mac.

Look for a settings menu, often labeled "Preferences," "Options," or "Settings." Find the option for two-sided scanning. It may be called "Duplex," "Two-Sided," "Both Sides," or "Double-Sided." Check that box or toggle it on. Some software also lets you choose whether to scan "long edge" or "short edge" — this refers to which way the page would flip if it were bound. For most documents, long edge is correct.

Once two-sided scanning is enabled, start the scan. The feeder will pull the first page through, scan it, and automatically flip it to scan the back before moving to the next page. The software will arrange the scans so that both sides of page 1 appear together, then both sides of page 2, and so on.

Scanning a flatbed scanner two-sided

Place your first page face-down on the glass, close the lid, and scan it through your software. When that scan finishes, remove the page and place the next page face-down. Repeat until you've scanned one side of every page.

Once you've finished the first side, physically flip your entire stack of pages over — so what was the back is now facing down on the glass — and scan the stack again in the same order. This time, your software will create a second batch of scans.

After both batches are done, you'll need to arrange them so that both sides of each page sit together. Most scanning software can do this automatically if you tell it you scanned two-sided. Look for an option like "Arrange two-sided pages" or "Interleave pages." If your software doesn't have this feature, you can manually reorder the pages in a PDF editor like Adobe Acrobat Reader or free tools like PDFtk or ILovePDF online.

Avoiding common mistakes when flipping pages

The most common error is flipping the stack the wrong way. If you scan pages 1–10 face-down, and then flip the stack so page 10 is now on top, you'll scan page 10's back first, then page 9's back, and so on — in reverse order. Your software won't know this happened and will pair the wrong backs with the wrong fronts.

To avoid this: after you finish scanning the first side, remove the scanned pages from the scanner and set them aside. Take your original stack, flip it so the unscanned side is now face-down, and place it in the scanner in the same position as before. This way, page 1 goes through first on the second pass, just as it did on the first pass.

Another mistake is changing the scanner settings between the first and second batch. If you scan the first side at 300 DPI and the second side at 150 DPI, the file sizes and quality won't match, and some software will refuse to combine them. Write down your settings before you start, and don't change them until both sides are complete.

When your software can't arrange pages automatically

If your scanning software doesn't have an automatic interleave feature, you'll end up with two separate PDF files or image batches — one for all the fronts and one for all the backs. You can combine and reorder them using free online tools or desktop software.

PDFtk (available free for Windows, Mac, and Linux) lets you merge and reorder pages from the command line. ILovePDF and Smallpdf both have online tools where you can upload your two PDFs, choose to interleave them, and read the result. If you're working with image files rather than PDFs, you can open them in a free tool like GIMP or use an online image-to-PDF converter that lets you upload images in a specific order.

Before you spend time reordering, check whether your scanner's software has a two-sided mode you missed. Many flatbed scanners do have this feature buried in an advanced settings menu, and using it will save you the reordering step entirely.

Checking your two-sided scan for errors

After you've scanned both sides, open the final file and flip through it page by page. Look for pages that are upside-down, backwards, or missing. If you find a problem, you can usually fix it without rescanning the entire document.

Most PDF readers and editors let you rotate individual pages. If a page is upside-down, right-click it and select "Rotate 180 degrees." If a page is backwards (mirrored), you may need to use a tool like Adobe Acrobat Pro or an online service to flip it. If a page is missing or in the wrong place, you can delete it or move it using the page-management tools in your PDF software.

Frequently Asked Questions

Do I need to scan both sides if I'm just taking a photo with my phone?

Phone camera apps don't have two-sided modes — you're taking individual photos. You can photograph one side of all pages, then photograph the other side of all pages, and then use an app like Adobe Scan or Microsoft Lens to arrange them into a single document. These apps often have a "multi-page" mode that lets you take photos in sequence and combine them automatically.

What if my scanner keeps jamming when I load two-sided pages?

Make sure pages are aligned straight in the feeder tray and that you're not loading too many at once. Check your scanner's manual for the maximum page count — many older ADF scanners handle only 20 to 30 pages at a time. If pages are curled or damp, flatten them under a heavy book for an hour before scanning. Clean the feeder rollers with a lint-free cloth slightly dampened with water.

Can I scan two-sided documents at different resolutions for the front and back?

Technically yes, but it's not recommended. Different resolutions can cause file size mismatches and make the document look inconsistent when you view it. Stick to the same DPI (usually 300 for text, 600 for fine detail) for both sides. If you need different quality levels, scan everything at the higher resolution — you can always reduce it later if file size becomes a problem.

What's the difference between long-edge and short-edge duplex?

Long-edge duplex flips the page as if it were bound on the left or right side (like a book). Short-edge duplex flips it as if it were bound on the top or bottom (like a notepad). For most documents, long-edge is correct. Use short-edge only if your original document is actually bound that way or if your software specifically recommends it.