PNG to PDF

How do you turn PNG images into a PDF with the right page size?

Choose PNG images or drag them into the tool, arrange their thumbnails, and convert the batch into one PDF. Each image becomes one page. Start with Fit to image when you want each page to follow its own image dimensions. Choose A4 or another fixed size when every page needs a defined paper format, then check Image fit before downloading.

For a worked example, take a 1200 × 1800 pixel PNG, leave rotation at zero, choose Fit to image, set Resolution to 300 DPI, and leave Page margin at zero. The code calculates PDF points as pixels × 72 ÷ DPI: the page is 288 × 432 points, or 4 × 6 inches. At 150 DPI it becomes 576 × 864 points, or 8 × 12 inches. The source pixels stay the same; only their physical placement changes.

Which paper sizes and orientations can you choose?

Page size has eight choices in total, including Fit to image and Custom. The fixed presets below use stored dimensions in PDF points; one point is 1/72 inch. These are page boundaries, not a promise that your printer can print without borders.

Fixed page presets used by the converter

Preset	Paper dimensions	Stored points
A4	210 × 297 mm	595.28 × 841.89
A3	297 × 420 mm	841.89 × 1190.55
A5	148 × 210 mm	419.53 × 595.28
Letter	8.5 × 11 inches	612 × 792
Legal	8.5 × 14 inches	612 × 1008
Tabloid	11 × 17 inches	792 × 1224

Custom exposes Width (mm) and Height (mm), with input bounds of 10 to 1000. Fixed pages offer Portrait, Landscape, and Auto (per image). Auto checks each image's effective width and height after rotation. A mixed batch can therefore contain portrait and landscape pages. Fit to image instead follows image dimensions directly and shows Resolution rather than orientation controls.

How do Contain, Cover, and Stretch change the image?

On fixed pages, Contain scales proportionally using the smaller of the available-width and available-height ratios. It keeps the whole image visible, with unused space along one axis when proportions differ. Use it for screenshots with important text at the edges. The space is unpainted page area rather than an added white image background.

Cover uses the larger ratio, filling the available area while allowing image edges to extend outside the page. Crop position arrows move the drawing, and Zoom ranges from 50% to 300%. Below 100%, the reduced drawing may leave space again. Stretch uses the available width and height independently, so circles can become ovals. Check the preview for each page rather than assuming all source images share an aspect ratio.

How do margins and DPI affect the finished document?

Page margin starts at zero and ranges to 50. Although the interface labels this value in px, the PDF engine uses the number directly as PDF points. In Fit to image, it adds twice the margin to each page dimension. On fixed pages, it subtracts twice the margin from the available width and height before fitting the image.

Resolution offers 72, 150, and 300 DPI only for Fit to image. It changes physical size without generating more pixels or applying a compression target. On a fixed page, effective print resolution comes from the source pixels and the area where they are drawn. Review the downloaded document at its intended print size; selecting a higher DPI cannot recover detail absent from the PNG.

Can you reorder, rotate, and customize individual pages?

The PDF follows thumbnail order, including images appended with + Add more. Drag to reorder; keyboard sorting is also configured through the thumbnail buttons. Each Rotate control advances clockwise by 90 degrees through four orientations. Rotation is applied while drawing the embedded image, avoiding a separate rotated-image export.

With two or more images and a fixed page size, select a thumbnail and enable Customize this image. It overrides orientation and fit for that image, with Cover positioning available when relevant. Page size and margin remain shared across the batch. Disable the checkbox to return that image to global settings. This lets a landscape diagram and a portrait screenshot use different layouts in one document.

Does transparency survive, and is conversion lossless?

Transparent logos, diagrams, and mockup shadows retain alpha transparency through pdf-lib's PNG embedding. The library writes RGB image data and, when needed, a separate grayscale soft mask, the SMask mechanism in ISO 32000-1. Transparent areas show whatever is behind them in the PDF viewer. The tool does not paint a solid background behind the PNG.

PNG data is decoded and compressed into PDF image streams rather than stored as the original PNG file. There is no JPEG conversion step, but the installed decoder converts to 8-bit RGB and alpha. Do not treat the PDF as an archive preserving original file bytes or 16-bit precision. PDF/A-1 (ISO 19005-1) prohibits transparency; this converter has no PDF/A export setting, so ordinary PDF output should not be assumed to meet an archival requirement.

When should you use PNG rather than JPG for a PDF?

PNG uses lossless compression and supports alpha transparency; JPEG uses lossy compression and has no alpha channel. PNG suits screenshots, diagrams, and logos where clean edges or transparent backgrounds matter. Converting an already blurred image does not reconstruct sharper text. The result here contains images, without OCR or searchable text extraction.

For photographic JPEG inputs, use JPG to PDF. To combine different image formats or use additional image processing options, open Images to PDF. To join the result with an existing document, use Merge PDF. PNG conversion alone does not guarantee a smaller file.

What should you check if conversion fails or the PDF looks wrong?

The picker accepts a PNG MIME type or a .png filename, but renaming another format does not make its bytes valid PNG data. Unsupported files are skipped at selection; decoding failures appear during conversion. Animated PNGs with multiple frames are rejected by the installed decoder. There is no configured batch-count or file-size cap in this path, but large decoded images consume browser memory. Reduce the batch if it fails.

Processing reads local file bytes and creates the PDF in browser memory. The Content Security Policy permits connections only to this site; conversion itself makes no network requests. After conversion, Download saves the PDF, Back to editing returns to the same images, and Convert another clears the batch. Review page order, clipped edges, transparency, and physical size before sharing the document.