Page size, orientation, margins and fit
Every picture gets a page of its own. A4 (210 by 297 mm) is the default and the usual choice outside North America. US Letter (8.5 by 11 inches) and US Legal (8.5 by 14 inches) are the common sizes in the United States and Canada, and A3 and A5 are the next larger and smaller steps of the A series. If the page should follow the picture, choose Same as the image. Each page then takes the picture's own size at the resolution you set, but never longer than 297 mm on the long side and never shorter than 2 inches. That suits screenshots and drawings.
Auto orientation turns each page to match its picture, so a landscape photo gets a landscape page and a portrait photo gets a portrait page, in the same PDF. Portrait or Landscape forces every page the same way. Margin adds space around the picture: Small is half an inch (12.7 mm) and Big is one inch (25.4 mm).
Fit inside shows the whole picture, centred, with the page colour around it. Fill and crop covers the whole page and cuts off whatever sticks out, which suits a photo used as a full page but cuts into anything near its edge. A picture that is stored as it is keeps its cut-off parts inside the file, hidden by the page edge. A small picture is enlarged to fit, and the tool tells you when that leaves it below 100 dots per inch.
Smaller file or original quality
A PDF page shows a picture at some number of dots per inch (DPI). A photo of 4000 by 3000 pixels, which is 12 megapixels, fills the height of a landscape A4 page (8.27 inches) with 3000 pixels. That is about 363 DPI. A screen or an office printer shows little more than 200 DPI, so many of those pixels are never seen but are still stored.
Smaller file (recommended) removes that surplus. A picture with more detail than the resolution you choose (150, 200 or 300 DPI, with 200 as the default) is reduced to it, and photographs are saved again as JPG at quality 84. The photo above, on A4 at 200 DPI, becomes 2205 by 1654 pixels, about 30 percent of the original pixel count. Flat graphics such as screenshots and logos, and pictures with transparency, stay lossless. The tool never makes a picture bigger: if saving it again would not make it smaller, the picture goes in as it is.
Original quality, no recompression stores the picture data of a JPG exactly as it is, byte for byte (only the hidden camera and location details are cut out), and the compressed data of a PNG without changing it. Formats that a PDF cannot hold, such as WebP and HEIC, are decoded and stored without loss, which makes them larger. Choose it when the PDF is going to a print shop, an archive or a program that asks for the full resolution.
Before you build, the tool shows an estimated size. Afterwards it shows the real size, and a list tells you how each picture was stored, at what size in pixels and at what DPI on the page.
What happens to each kind of picture
- JPG: goes in as it is when you choose Original quality, and is turned upright by the page using the camera's orientation tag instead of being saved again. See JPG to PDF.
- PNG: the compressed data is copied without any change when the PNG has no transparency. Transparent areas show the page colour. See PNG to PDF.
- WebP, HEIC, AVIF, TIFF, BMP and SVG: a PDF cannot hold these, so they are decoded on your device and the pixels are stored again. See WebP to PDF.
- GIF and animated PNG: only the first picture is used. A TIFF file with several pages gives one picture. An SVG is drawn as large as its page can show.
The result is a PDF of pictures. Text inside a screenshot or a scan stays part of the picture, so it cannot be selected or searched.
Big sets, and pictures that are refused
Pictures are processed one at a time and each one is released before the next, so the memory in use stays low however many you add. What does build up is the finished PDF, which lives in your browser's memory until you download it. The tool warns when the estimate passes a limit that depends on your device, about 250 MB on a computer with plenty of memory and about 60 MB on a phone, and warns more strongly at about 600 MB and 150 MB. If a set is too big, make two PDFs and join them with Merge PDF.
A picture can be up to 100 megapixels. A file that is empty, damaged, cut short or not a picture is marked on its own row with the reason, and the others still go into the PDF. You can press Cancel while the PDF is being built.