How to Combine Multiple PNG Images Into One PDF (on Windows)

You have a folder of PNGs — screenshots, scans, photographed receipts — and somebody needs them as one PDF, in the right order. The short version: use a tool that merges locally, and fix the file ordering before you convert, because that is the step that actually goes wrong.

The short answer

1. Open the Image to PDF tool from the BizTray tray menu.
2. Drag in your PNGs, or the whole folder holding them.
3. Switch the output from one PDF per image to merged.
4. Drag the thumbnails into the order you want them read.
5. Pick an output folder and convert.

You get a single PDF, one image per page, with no watermark and nothing uploaded. If you only want each PNG as its own separate PDF, the PNG to PDF converter covers that case directly.

The part everyone gets wrong: file order

This is the failure that produces a PDF nobody can read, and it has nothing to do with the converter.

Windows sorts file names as text. That means image10.png sorts before image2.png, because it compares character by character and 1 comes before 2. Drop twelve screenshots into any tool that trusts the folder order and you get pages 1, 10, 11, 12, 2, 3 — technically sorted, completely wrong.

There are two fixes:

• Zero-pad the numbers. Rename to image001.png, image002.png, image010.png. Now text order and numeric order are the same thing, and every tool that touches the folder gets it right from then on. Worth doing if the folder will be reused.
• Set the order by hand. Drag the thumbnails into place before converting. Faster for a one-off, and it does not touch your files.

If the images came off a scanner or a phone, check the order rather than assuming it. Scanners often number sequentially but start wherever the last job finished.

Why the obvious way is worse

The first result for this problem is always a website that asks you to upload your images. It works, and there are three costs that are easy to miss:

• The limits are the business model. Three files an hour, 10 MB a file, a watermark unless you subscribe. Those caps exist because every conversion costs the operator real server time — the constraint is real, it is just theirs rather than yours.
• You handed over the documents. Screenshots and scans are the things most likely to have an account number, an address or a signature sitting in the corner. Uploading is a decision worth making deliberately.
• The re-encoding. Some web converters recompress your PNGs to JPEG on the way through to keep their own bandwidth down. On a photo you may not notice; on a screenshot full of text and sharp edges, you will.

Windows itself offers a partial escape: select the images in File Explorer, right-click and choose Print, then pick Microsoft Print to PDF. It is free and already installed. It also gives you no control over ordering beyond the selection, adds printer margins you did not ask for, and quietly scales images to fit the paper size. Fine for four screenshots; painful for forty.

Doing it on your own machine

The reason a local tool has no quota is that there is no server to meter. The conversion uses your own CPU, so the number of files and their size stop being somebody's cost centre and become just a question of how fast your disk is.

That changes what is reasonable to attempt. Merging 300 scans into one PDF is not a special case that needs a paid tier — it is the same operation as merging three.

A few things worth knowing before you run it:

• Transparency becomes white. PDF pages have no alpha channel, so any transparent region in a PNG is composited onto a white background. That is the right default for anything you intend to print or send. If you need the transparency, keep the original PNG too — it is never modified.
• Quality is preserved. The image is embedded rather than converted to a lossy format, so nothing is thrown away. The trade is file size: a merged PDF of high-resolution screenshots is genuinely large, and that is expected.
• Rotation is read from the file. Photos carry an EXIF orientation flag rather than physically rotated pixels. That flag is honoured, so portrait photos stay portrait instead of landing on their side.

The Image to PDF utility handles the whole job — PNG, JPG, HEIC, WebP, TIFF and BMP can all go into the same merge, so a folder of mixed screenshots and phone photos does not need sorting by format first.

If it is the same folder every time

If this is a recurring job — a scanner that always writes to one place, a screenshot tool with a fixed output folder — a Watch Folders rule can point at that folder and convert new arrivals without you opening the app again.

It is worth setting up only once the folder is genuinely repeat business. For a one-off merge, the manual route above is quicker than configuring a rule.

A note on why this is free

BizTray has no subscription, no quota and no watermark, which reasonably prompts the question of what pays for it. The answer is that it shares a portion of your spare internet bandwidth through a vetted partner rather than charging you. It relays other parties' web traffic and never touches your documents.

There is a real trade attached: sharing can be switched off from Settings or the tray, and the tools do not run while it is off. The full explanation, including the parts you might not like, is on How it's funded.

Related conversions

• PNG to PDF — one PDF per image, or merged.
• JPG to PDF — the same job for photos and scans.
• HEIC to PDF — iPhone photos, without installing a codec.