Images to PDF

How Images to PDF Works

ConvertUnlimited uses jsPDF (version 2.5.1) to generate PDF documents directly in the browser. When an image is added, it is read and decoded locally; the tool then draws each image onto an HTML5 canvas and embeds the result into a PDF page sized by the chosen orientation, page size, and margin.

Selected file contents are processed locally in your browser for this workflow. ConvertUnlimited does not provide a server-side upload endpoint for it.

Every image is re-encoded as JPEG, and transparency is flattened to white

This is a real behavior worth knowing before you rely on it for a specific use case. Regardless of the source format, JPG, PNG, or WebP, every image is drawn onto a canvas, filled with a solid white background first, then exported with canvas.toDataURL("image/jpeg", 0.95) before being embedded in the PDF at a fixed 95% JPEG quality. Concretely, this means:

• A transparent PNG or WebP (a logo, an icon, an exported UI graphic) loses its transparency: any transparent area becomes solid white in the PDF, with no option to choose a different background color.
• PNG's lossless pixel data is not preserved in the output PDF. Even a screenshot or diagram with sharp text edges goes through the same fixed-quality JPEG re-encode as a photo, which can introduce mild fuzziness or ringing around hard edges compared to the original PNG.
• The 95% JPEG quality setting is fixed and is not exposed as a control in the interface.

If a PNG's transparency or exact pixel edges need to survive, keep it as a standalone image file, or flatten it against your intended background color yourself before adding it here.

Page sizes and margins

"Auto-fit" currently renders at standard A4 dimensions rather than sizing the page to each image's own dimensions. If you need a page that matches an image's own proportions closely, pick A4 or Letter, whichever is closer to your image's aspect ratio, and use the None margin option.

Margin options are None (0 mm), Small (10 mm), and Medium (20 mm), applied evenly on all four sides of the chosen page size.

Small images are enlarged to fill the page

Each image is scaled by the largest ratio that fits it inside the printable area (page size minus margins) while preserving its aspect ratio. That scaling ratio is not capped at 100%: an image smaller than the printable area — a small screenshot or a low-resolution photo — is enlarged to fill as much of the page as its aspect ratio allows, which can make a low-resolution source look visibly soft or blurry once printed at page size. For predictable results, use source images at least as large as your target page size at 150 to 300 DPI (see the DPI table on the Image Resizer page).

Why Combine Images into PDF?

• Document Organization: Group related photos (receipts, IDs, homework) into a single file.
• Compatibility: PDF is a broadly supported document format that opens consistently across devices.
• Email Friendly: Most email clients handle one PDF attachment more predictably than several separate image files.
• Printing: A PDF preserves the page layout and scale so images print at the intended size.

Failure modes and limits

• Unsupported formats. Only JPG, PNG, and WebP are accepted; GIF, SVG, BMP, HEIC, and PDF inputs are rejected outright.
• Very large batches. Each added image is held as a base64 data URL in memory (roughly a third larger than the original file) alongside the in-progress PDF, so 50 or more high-resolution photos can exceed a browser tab's available memory.
• Rotation combined with page overflow. Rotating an image 90 degrees swaps its effective width and height before the fit calculation runs, which can change how much a given image is enlarged or shrunk to fit the page.
• Mobile devices. Phones and tablets have less available memory; keep batches smaller than on a desktop browser.

Local Browser-based PDF Generation

ConvertUnlimited provides the PDF-generation logic as a static script that runs in this tab, rather than uploading files to a server for processing, as some "online PDF" tools do.

Frequently Asked Questions

Is there a page limit?

We don't impose a limit, but very large batches (50+ high-resolution photos) may exceed your browser's allocated memory. If the tab becomes unresponsive, try creating smaller PDFs.

Can I reorder the images?

Yes. Simply use the individual "Move Up" or "Move Down" buttons (or remove images) to adjust the sequence before generating the final PDF.

Will my images lose quality?

Every image is re-encoded as JPEG at a fixed 95% quality before it is embedded, regardless of the source format, and any transparent areas are filled with solid white first. Images smaller than the page's printable area are also enlarged to fill it, which can look soft for low-resolution sources. See the sections above for the full technical detail.

Does the PDF preserve transparency from a PNG or WebP source?

No. Every image is flattened onto a solid white background before being embedded, since the tool always exports through a JPEG re-encode step regardless of source format.

What does "Auto-fit" page size actually do?

It currently uses standard A4 dimensions rather than sizing the page to each image's own dimensions. Choose A4 or Letter directly based on which is closer to your images' proportions.

Can I mix images with different sizes and orientations in one PDF?

Yes. Each image is placed on its own page and scaled independently to fit the chosen page size, so a mix of portrait and landscape source photos is supported.

Browser Support

This tool works in all modern browsers supporting the HTML5 Canvas API and File API, including Chrome, Firefox, Safari, and Edge.