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How to Convert PNG to PDF

By Clioos 团队

The free offline way is Pillow: each PNG becomes one PDF page, no upload, no account. Tested 2 November 2026 with Pillow 13.0.0 — two sample PNGs (1240x1754 at 12,179 bytes and 800x1000 at 6,571 bytes) became a 2-page PDF of 100,751 bytes. Clioos does not offer a PNG-to-PDF tool — this guide teaches the method.

At a glance

Clioos has no PNG-to-PDF tool. The method below runs on your own computer with free, open-source Pillow — no upload, no account.
Each PNG becomes one PDF page, in file order. Two PNGs in, two pages out in the test.
The output PDF was larger than the PNGs combined (100,751 vs 18,750 bytes) because Pillow re-encodes the images — PNG compresses flat graphics very well, so do not assume the PDF will be smaller. Check the output size.
Page size follows the image dimensions at the resolution you set (150 DPI in the test; pages came out A4, 595.2 x 841.92 pts).
A PNG-to-PDF conversion does not OCR anything: the PDF pages are pictures, not searchable text.

Steps

Install Pillow: pip install pillow (Pillow 13.0.0 in the test).
Run: Image.open(first).save("out.pdf", "PDF", save_all=True, append_images=rest, resolution=150.0).
Verify: open the PDF and count the pages (2 in the test), then compare sizes — input 18,750 bytes, output 100,751 bytes.
If a page looks wrong, re-run from the original PNGs — never re-convert the PDF.

Worked example (tested 2 November 2026)

Test files: two generated sample PNGs (flat graphics with line patterns). Method: Pillow 13.0.0, one image per page, 150 DPI.

File	Dimensions	Size
shot1.png	1240x1754	12,179 bytes
shot2.png	800x1000	6,571 bytes
shots.pdf (output)	2 pages, A4	100,751 bytes

Total PNG input was 18,750 bytes; the PDF came out larger (100,751 bytes) because the images were re-encoded. Page count matched the image count exactly: 2 in, 2 out.

Which method to pick

Offline (Pillow, this guide): free, private, scriptable. Needs Python installed.
Browser converter: no install, drag and drop — but your images upload to a vendor server.
OS print to PDF: built into most systems for single images, but page control is weaker than a script.

What it can't do

No Clioos tool for this: Clioos does not offer PNG-to-PDF conversion. The method above is the free offline route.
No OCR: the PDF pages are pictures. Text in the images is not searchable or selectable.
Size can go either way: in this test the PDF was larger than the PNGs. With photographic PNGs it may be smaller. Always check the output.
No editing: this only packs images into pages. Cropping, rotating or reordering means editing the images first.
No encryption: the output PDF is unprotected; password protection needs another tool.

Frequently asked questions

Is it free to convert PNG to PDF?

Yes, with Pillow — free and open source, no per-file charge. Browser tools are free up to a daily limit.

Will the PDF be smaller than the PNGs?

Not necessarily. In this test it was larger (100,751 vs 18,750 bytes) because flat PNG graphics compress extremely well and the PDF re-encodes them. Check the output size.

Can I control the page size?

Yes: page size follows the image dimensions at the resolution you set (150 DPI in the test). Larger images make larger pages.

Does the PDF text become searchable?

No. The pages are pictures of the PNGs. Searchable text needs OCR as a separate step, and OCR quality depends on the image.