Before writing a line of PDFImageMerger, the obvious question was whether this already existed. It does, many times over, and some of those tools are genuinely well built. This isn’t a “the others are bad, use mine” post — it’s the actual comparison, including the parts where PDFImageMerger is the wrong tool for the job.
Important
Get this out of the way first, because it shapes everything below: PDFImageMerger only merges images into a PDF. No OCR, no text editing, no forms, no e-signatures, no redaction, no watermarking, no splitting or reordering pages after the fact. One input, one operation, one output. Every tool in this comparison does more than that — the question is whether you need the “more.”
The lineup
Adobe Acrobat. The reference point everyone measures against. Genuinely powerful — OCR, e-signatures, redaction, form creation, text and image editing inside existing PDFs, cloud sync through Adobe Document Cloud. Also genuinely expensive: Acrobat Standard runs around 19.99/month, billed annually — cheaper month-to-month plans exist but cost more overall. Windows, macOS, web and mobile; no native Linux desktop app.
Smallpdf. A polished browser-based tool. The free tier caps you at a couple of tasks a day; unlimited use sits behind a subscription, roughly 6/month billed annually. Being browser-based, it technically runs anywhere with a browser — but every file you merge gets uploaded to Smallpdf’s servers first.
iLovePDF. Smallpdf’s closest sibling in both function and business model — free tier with daily limits and ads, premium around $4–6/month on annual plans. Same upload-based architecture, same trade: convenience in exchange for your files passing through someone else’s infrastructure.
PDF24 Creator. A genuinely free, feature-dense desktop suite from Geek Software — merge, split, convert, basic OCR, and a fair amount more, no subscription. The catches: Windows only, closed source, and the installer has historically bundled optional extra offers you need to watch for and decline during setup.
img2pdf. The closest thing to a direct technical relative. Free, open source, Python-based, and it does the same lossless embedding trick PDFImageMerger’s “don’t modify images” mode does — JPEGs go in byte-for-byte, no re-encoding. Runs anywhere Python does. Entirely a command-line tool — no window, no button, no drag and drop. Everything is a flag and an invocation.
macOS Preview. Built into every Mac, free, and capable of combining images into a PDF by dragging thumbnails into its sidebar and exporting. No install, but macOS-only, entirely manual, and no control at all over page format, resolution, compression or output size — you get what Preview decides to give you.
PDFImageMerger. Free, open source (MIT), local-only — nothing uploaded, nothing installed beyond a portable download — for Linux (AppImage) and Windows (portable). Does one thing: merges images into a PDF, with real control over page format, resolution, compression and a size estimate before you commit.
Side by side
| Adobe Acrobat | Smallpdf | iLovePDF | PDF24 Creator | img2pdf | PDFImageMerger | |
|---|---|---|---|---|---|---|
| Cost | $13–20/mo | Free tier + ~$6–9/mo | Free tier + ~$4–6/mo | Free | Free | Free |
| Open source | No | No | No | No | Yes | Yes (MIT) |
| Platforms | Win/macOS/web/mobile | Any browser | Any browser | Windows only | Anywhere with Python | Linux, Windows |
| Interface | GUI | Web | Web | GUI | Command line only | GUI |
| Files leave your machine? | Yes (cloud sync) | Yes (upload) | Yes (upload) | No | No | No |
| Only merges images? | No — full PDF suite | No — full PDF suite | No — full PDF suite | No — full toolbox | Yes | Yes |
| Real size estimate before building | No | No | No | No | No | Yes |
| Lossless option | N/A (re-encodes) | N/A | N/A | Varies | Yes | Yes |
Where PDFImageMerger genuinely isn’t the answer
If you need to make a scanned document’s text searchable, fill in a form, add an actual signature, redact a paragraph, or edit text that’s already sitting inside a PDF — that’s Acrobat’s territory, and none of the other tools on this list touch it either. PDFImageMerger doesn’t pretend to; it only ever sees images, never text.
If you’re comfortable at a terminal and already have a script built around img2pdf, there’s no reason to switch to a window and some buttons for something you’ve already automated. Keep your pipeline.
If you’re on macOS and it’s a genuine one-off — three photos, once, never again — Preview is sitting right there and costs you nothing extra to open.
Note
If what you actually need is the free-and-fast convenience of a browser tool for something low-stakes — a couple of holiday photos, nothing sensitive — Smallpdf or iLovePDF’s free tier will get it done in under a minute. The trade only starts to matter once the files involved are things you’d rather not hand to a server.
Where PDFImageMerger fits
It exists for the space between “I’ll just upload it, it’s fine” and “I need a $240-a-year subscription to combine six photos.” Free, local, no account, no daily task limit, no watermark on the free tier because there is no tier — and, unlike the browser tools, no trust required in a privacy policy, because there’s no upload for a privacy policy to govern.
Tip
Rule of thumb: need OCR, forms, signatures or real editing → Adobe Acrobat. Already scripting img2pdf → keep doing that. One-off on a Mac → Preview. Just need images merged into a PDF, for free, without your files leaving your computer → PDFImageMerger.
Get PDFImageMerger on GitHub — free, open source, Linux and Windows.