How to Add an Image to a PDF: Logos, Photos and Stamps on Any Page
Adding an image to a finished PDF sounds like it should require a full editor, but most real cases are simpler than that. You need a logo in the header of a quote you received as a PDF, a passport photo in the box on an application form, a scanned company seal next to a signature, or a small product photo in a spec sheet. In every one of those cases you are placing a picture at a specific spot on a specific page, not restructuring the document. That is exactly what the sign tool does.
The sign tool accepts an uploaded image alongside its drawn and typed options, and once the image is loaded you can position it anywhere on any page. Nothing about it is limited to handwriting. Upload a PNG of your logo and drop it into the header. Upload a photo and place it in the application form box. Upload a scan of a red company seal and set it partly overlapping the signature line, the way a physical chop would sit. Then export, and the picture is part of the page.
Image preparation matters more than placement technique. Use PNG with a transparent background for logos and seals so the white rectangle around them does not cover the ruled lines underneath. If your logo only exists as a JPG on a white background, the artefact you will notice is a pale box on any coloured or shaded area of the page. Crop tight to the artwork before uploading so that positioning corresponds to what you actually see, rather than to a large invisible margin around it.
For sizing, resist the urge to make the image large. A logo in a document header usually sits somewhere between two and four centimetres wide; anything bigger reads as amateur. A passport photo should match the printed box exactly, so measure the box against a known reference such as the width of a standard form field, then adjust in small steps and zoom in to check the fit. If the source image is high resolution, the file will grow noticeably, so run the finished document through compress before sending it.
One caveat worth knowing. Placing an image is an overlay operation, so it sits on top of whatever is already there rather than pushing text aside. If you drop a logo over a paragraph, the paragraph is hidden but still present in the file, exactly like a white-out box. That is harmless for decorative work but is not a way to conceal information; for that you need redact. And if you are building a document mostly out of pictures in the first place, Image to PDF is a faster starting point than adding them one by one.