Convert PNG to PDF
Converting PNG to PDF places each PNG image on its own PDF page while keeping the lossless pixel data intact. This tool does the conversion locally in your browser: screenshots, diagrams, and graphics stay pixel-perfect, alpha transparency is handled, and nothing is uploaded. Drop in one or more PNG files, choose a page size, and download a single PDF.
How it works
PNG and PDF share a compression algorithm. PNG stores its pixels with Deflate (the zlib/gzip family), and PDF exposes the identical algorithm as its FlateDecode filter. So a PNG's image data can move into a PDF losslessly: the tool decodes the PNG's scanline filters, then stores the raw pixels Flate-compressed inside an image XObject. No quantization, no JPEG artifacts — a 1-pixel-wide line stays a 1-pixel-wide line.
Transparency needs one extra step, because a PDF image XObject has no alpha channel of its own. If your PNG has an alpha channel (RGBA or grayscale-alpha), the tool splits it off into a separate grayscale image and attaches it to the color image as an SMask (soft mask). PDF viewers multiply the two together at render time, so anti-aliased logo edges and semi-transparent drop shadows composite cleanly over the page background instead of getting a jagged halo. Fully transparent regions simply show the page — white, unless you place the image over other content.
Each image then gets its own page. The page's media box is either matched to the image dimensions or set to a standard size like A4 or Letter with the image scaled to fit; scaling is a matrix in the content stream, so no pixels are resampled. The whole document is assembled with pdf-lib in browser memory and saved from your device — the images are never transmitted anywhere, which is worth knowing when your screenshots contain dashboards, chat logs, or account details.
Worked example: 8 screenshots into a review document
Eight full-screen captures from a 2560 × 1440 monitor, saved as PNG at an average of 610 KB each (4.9 MB total), converted with "one image per page, fit to A4 landscape". The output is an 8-page PDF of 4.93 MB, generated in under two seconds. Because PNG data passes through losslessly, zooming to 400% in the PDF shows exactly the same pixels as the original captures — menu text stays sharp instead of blooming into JPEG mosquito noise.
For comparison, converting the same captures to JPEG at quality 80 before making the PDF produced a 3.1 MB file, but the small UI text showed visible ringing at 200% zoom. The rule of thumb from this example: keep PNGs as PNGs when the content is text and interface chrome; the ~40% size saving from JPEG is rarely worth the legibility loss, and if size matters you can shrink the finished file with Compress PDF instead, choosing the quality consciously.
PNG to PDF — frequently asked questions
Is PNG to PDF conversion lossless?
Yes. PNG uses Deflate compression and PDF supports the same algorithm through its FlateDecode filter, so the pixel data is carried over without any lossy re-encoding. Text in screenshots stays as crisp in the PDF as in the original image.
What happens to PNG transparency in a PDF?
The alpha channel becomes a soft mask (SMask) attached to the image inside the PDF, so transparent regions show whatever is behind the image — normally the white page. Semi-transparent shadows and anti-aliased edges are preserved rather than turning into hard black or white fringes.
Are my PNG files uploaded anywhere?
No. The PDF is assembled by JavaScript running on your device and never touches a server. The page even keeps working if you go offline after it loads.
Should I use PNG or JPG when making a PDF of screenshots?
PNG. Screenshots contain sharp edges and flat colors, which JPEG compression smears into visible artifacts around text. PNG keeps those edges exact, and for typical UI screenshots the file is often smaller than a high-quality JPEG anyway.
Can I put several PNG images into one PDF?
Yes. Each image becomes one page, in the order you set before converting. A sequence of screenshots turns into a single scrollable, printable document.