A PDF made from images is a container: each page holds one picture. The images keep their own encoding, so a good conversion adds no quality loss at all.
The decisions that matter are page size and how images that do not match it are fitted. Getting those wrong produces white margins, cropped edges or a file three times larger than it needed to be.
Receipts photographed on a phone that have to go in as one expense claim. A set of scans that needs to be a single document. Screenshots for a bug report. Images are convenient to capture and awkward to send in bulk, and a PDF fixes that by giving them one file and a fixed order.
What the PDF actually contains
Each image becomes a page, and on that page the image is placed as a single object with a position and a size. A well-built converter embeds the original compressed data directly, so the JPEG that came off your phone is the same JPEG sitting inside the PDF.
That is why a straightforward image-to-PDF conversion costs nothing in quality. Nothing is decoded and re-encoded. The pixels are identical, just wrapped in a page.
A good converter embeds the original image data rather than re-encoding it.
Slightly larger than the images together, because each page adds structure.
The pages are pictures. Searching finds nothing until OCR adds a text layer.
Page size and fitting
Photographs are not A4 shaped. A phone camera produces a 4:3 or 3:2 rectangle, a screenshot matches your display, and a scanned receipt is long and narrow. The converter has to reconcile that with a page.
One page per image, exactly
- No white margins anywhere
- Nothing is cropped or scaled
- Every page can be a different size
- Good for screenshots and mixed sources
- Prints awkwardly, since sizes vary
Everything on A4 or Letter
- Consistent, predictable printing
- White margins where shapes do not match
- Scaling down slightly softens fine detail
- Good for anything destined for paper
- Mixed orientations still need handling
The rule that works: if the document will be printed or filed alongside other paperwork, use a fixed page size. If it will only ever be read on a screen, matching each page to its image avoids margins and keeps everything at full size.
Getting the order right
The same filename sorting problem that affects merging affects this. Images named IMG_2.jpg and IMG_10.jpg sort with ten before two, because text is compared character by character.
Phone cameras usually avoid this by using long padded numbers, but anything renamed by hand or exported from an app with a simple counter will scramble past nine files. Either pad the numbers or arrange the images deliberately in the converter before building the file.
Keeping the file reasonable
Modern phone photographs are large. A twelve megapixel image is several megabytes, and twenty of them make a PDF that no email will accept.
The important thing to understand is that a photograph of a document contains far more detail than the document needs. A page of text captured at twelve megapixels is roughly 600 DPI, which is an archival scanning resolution. Reducing that to 300 DPI, which is print quality, cuts the data by three quarters and changes nothing you can see.
- Screen reading only150 DPI
- Ordinary printing300 DPI
- Archival reproduction600 DPI
- A phone photo of A4Around 600 DPI
- ScreenshotsNative size, do not scale
- Receipts for expenses200 to 300 DPI
Making the result searchable
A PDF built from images contains no text, only pictures of text. Searching finds nothing, copying is impossible, and screen readers have nothing to work with.
Optical character recognition solves this by reading the shapes and writing an invisible text layer behind each image. The page looks identical and becomes searchable. Worth doing for anything that will be filed and looked for again, and unnecessary for a one-off set of screenshots.
Turn images into a PDF
Drop in JPGs or PNGs, set the order, and download one file. Runs entirely in your browser.
Common questions
The decisions behind the output.
01Does converting images to PDF reduce quality?
It should not. A good converter embeds the original compressed image data directly, so the pixels in the PDF are identical to the pixels in the source files. If the output looks softer, the tool re-encoded the images, which is unnecessary.
02Why are there white margins around my images?
Because the page size does not match the image shape. A photograph on an A4 page leaves space at the edges. Either choose a page size that matches each image, or accept the margins if the document is destined for print.
03Why are my images in the wrong order?
Filename sorting. Text is compared one character at a time, so IMG_10 comes before IMG_2. Pad the numbers so they are the same length, or arrange the images manually in the converter before building the file.
04Why is my PDF so large?
Because phone photographs are large and a PDF of twenty of them is the sum of twenty large files. A photo of a document typically carries around 600 DPI of detail when 300 is plenty, so compressing the finished PDF usually halves it or better with no visible change.
05Can I search the text in a PDF made from photos?
Not until OCR adds a text layer. The pages are pictures of text rather than text, so there is nothing for search to find. Running OCR writes invisible text behind each image and makes the document searchable without changing how it looks.
06Should my screenshots be JPEG or PNG?
PNG. JPEG compression is designed for photographs and puts visible artifacts around the hard edges of text and interface elements. PNG keeps screenshots crisp, and for an image with large flat areas of colour it is often smaller as well.