Quality or file size: choosing how images go into the PDF

2026-10-04

Image to PDF has two quality options in Page setup: Quality first, the default, and Smaller file. Neither one changes the order, the pages or the page size — only how each image is stored inside the PDF. Details under the options gives the short version of what follows.

What happens to each kind of image

With Smaller file, a large image’s long side becomes 2000 px — a very long or wide image, such as a scrolling screenshot or a panorama, keeps at least 600 px on its short side instead, so it stays readable — and photos are saved as JPG at a lower quality than with Quality first. Smaller file only uses the new version of an image when it really is smaller than the Quality first version. Otherwise that image goes in exactly as it would with Quality first — images are never enlarged. How much a PDF shrinks depends entirely on your images, so there is no fixed percentage to expect.

Quality first

Quality first keeps as much of each image as it can:

• Most JPG photos are not re-encoded. Their image data goes into the PDF unchanged; only hidden details such as location and camera information are removed. This covers ordinary 8-bit colour and greyscale JPGs. A JPG in CMYK colour or with 12 bits per channel is decoded and saved again as high-quality JPG, and its card shows Re-encoded as JPG.
• PNG, screenshots and lossless WebP stay lossless, so text and sharp edges get no compression blur.
• HEIC and lossy WebP are converted to JPG, because they are decoded first. The card shows HEIC → JPG or WebP → JPG.

Lossless is about how the pixels are stored, not how many there are. An image your browser has to decode — PNG, WebP, HEIC or one of those special JPGs — is scaled down when it has more than about 16.7 million pixels, because that is a common limit for a browser’s drawing surface. Its card then says Scaled down to fit the device limit. JPG photos that go in directly are not affected by this limit.

Smaller file

Smaller file is useful for a PDF you will email or upload to a form with a size limit. The long side of a reduced image is at most 2000 px — on an A4 page that is roughly 170 dots per inch, enough to read ordinary text in a photographed document. Long screenshots and panoramas keep at least 600 px on their short side, so their text stays readable.

The cost is resolution: fine print and small details can look softer, and zooming in shows less. PNG, screenshots and images with transparency are never turned into JPG; they are only made smaller, and only when that actually reduces the size.

See the real size before you share

After you tap Save PDF, the strip at the bottom shows PDF ready, the number of pages and the real size of the file. It also tells you how many images were converted to JPG and how many were scaled down.

To compare, save once with Quality first, then switch to Smaller file and save again — a changed setting makes a new PDF. Download again only gives another copy of the last one.

Which one to choose

• Keep Quality first for photos you want to print or zoom into, scans of documents with small print, and anything you will archive.
• Choose Smaller file when a size limit matters more than the last bit of detail.
• Screenshots stay lossless either way; for them, the page size often matters more — see A4, Letter or fit to image.

What the PDF keeps beyond the pixels — transparency, colour profiles, metadata — is covered in what changes when images become a PDF.