Combine images into a PDF

No. This puts a picture on each page, so a scan of a printed document arrives as an image of that document - you can read it, but you cannot select the words or search for them. Making text searchable means recognising the characters and storing them as text, which is a different job. The text extractor on this site does the recognition part, and it also runs entirely in your browser.

Photographs are re-encoded once as JPEG, at the quality you choose, and those bytes are written into the PDF unchanged - a PDF can carry JPEG data directly, so there is no second compression on top. If your source was already a JPEG, that is one extra lossy generation, which at quality 85 is not usually visible. If you cannot accept even that, the lossless option skips JPEG entirely at the cost of a much larger file.

For screenshots, scanned text, diagrams, line art and anything with hard edges. JPEG compression puts faint ringing around high-contrast boundaries, which is invisible in a photograph of a face and very visible around small black text on white. The lossless route stores the pixels exactly, usually at several times the file size - which is still often smaller than you would expect, because pages of text compress well.

Because A4 is a fixed shape and your image probably is not, so fitting it inside without distorting it leaves space. The page is centred with a margin, which is what a printer expects. If you would rather have no border at all, choose the page size that fits the image, and each page becomes exactly the shape of the picture on it.

Yes. The list shows the order they will appear in, and each entry can be moved up or down. Files dropped in later are added to the end rather than replacing what is already there, so you can build the document in stages - a folder of scans first, then the cover page.

No. The PDF is assembled byte by byte inside this page, from images your browser decoded on your device. There is no PDF library downloaded from anywhere and no server involved, and a content security policy the browser enforces prevents this page from sending your files to another domain.