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Image to PDF

PDF Tools · Updated

Combine a set of images into a single PDF, with control over page size, orientation and order. The whole thing runs on your own machine: the images are decoded, laid out and written into a PDF in the browser, and nothing is uploaded.

Up to 50, each under 30.00 MB. They become pages in the order below.

Orientation

On all four sides

Lower is a smaller file and a softer image

How to use the image to pdf

  1. 1Choose your images. They become pages in the order shown, and the arrows reorder them.
  2. 2Pick a page size, or let each page fit its own image.
  3. 3Set the margin and the JPEG quality — the quality decides the file size.
  4. 4Build the PDF and download it. The table shows the effective resolution of each page.

Examples

Photographs of a document

Input
Four phone photos at 4032 × 3024
Result
A four-page A4 PDF, each image landscape and centred inside a 10 mm margin

Fitting the page to the image

Input
A single 1200 × 628 banner at 96 dpi
Result
A one-page PDF sized to the image rather than to a paper standard

About the image to pdf

How the file is built

A PDF holding only images is a genuinely simple document: a catalogue pointing at a page tree, then for each page an object describing its size, a short content stream placing the image, and the image itself. The image object uses the DCTDecode filter, which means the JPEG bytes are stored as they arrive rather than being decompressed and recompressed.

That is the whole reason this can be done without a PDF library. The parts of the format that are genuinely hard — fonts, text layout, encryption, incremental updates — are the parts a picture-only document never touches.

Page size, margins and what they cost

Choosing a standard page size gives you a document that prints predictably, at the price of fitting the image into a shape it was not. Fitting the page to the image does the opposite: no letterboxing, but a PDF whose pages are all different sizes, which some printers and viewers handle awkwardly.

Margins are worth keeping even when nothing is printed in them. Many printers cannot print to the edge of a sheet and will scale a full-bleed page down to fit, which shrinks the image slightly and moves it off centre — a 10 mm margin costs a little image area and avoids that entirely.

Frequently asked questions

Are my images uploaded anywhere?
No. The images are decoded, drawn to a canvas and written into a PDF entirely by JavaScript running on your machine, and the finished file is created in memory and handed to your browser's downloader. Nothing is sent to a server, which matters here because the things people most often turn into PDFs are exactly the documents that should not be passing through an unknown one.
Why are PNG images re-encoded as JPEG?
Because a PDF can carry JPEG data with no further processing — the compressed bytes go in as they are — and that is what keeps this tool a few hundred lines rather than a few hundred kilobytes of library. It does mean a PNG becomes lossy at this step, and any transparency is flattened onto white, since a PDF page has no alpha channel behind the image. The quality slider is there to control that trade.
What resolution will the PDF print at?
The table after building shows it per page. Effective resolution is the image's pixel width divided by how wide it is placed, so the same photo is higher resolution on A5 than on A3. Below about 150 dpi a photograph looks soft in print; 300 dpi is the usual target. Enlarging a small image cannot add detail that was never captured, so the fix is a bigger original or a smaller page.
Can it merge existing PDFs or add text?
No. This writes a PDF containing images and nothing else — no text, no fonts, no vector drawing, no encryption, and no reading of an existing PDF. Those are separate jobs, and the other PDF tools listed on this site are still being built.

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