Most signatures are added as annotations, a layer above the page. Whether they display depends on the reader honouring that layer, and not all of them do.
Flatten the document after signing. The signature becomes ordinary page content and every reader shows it, because there is no longer anything optional about it.
This failure is particularly awkward because it is invisible from your side. The document looks signed on your screen, and you have no way of knowing it arrived blank unless someone tells you.
Why a signature can be optional
A PDF page has content, and it can also carry annotations: comments, highlights, stamps, form fields and drawn marks. Annotations sit above the page rather than in it, which is what makes them removable without disturbing the document underneath.
That flexibility is the problem. Because annotations are a separate layer, readers decide whether to draw them. Full readers do. Simple viewers, some mobile apps, some embedded previews and some print paths do not, or draw only certain kinds.
Above the page, as a stamp or drawing rather than page content.
Simple viewers and some print paths skip annotations entirely.
The signature becomes page content, with nothing optional about it.
Three things called a signature
The word covers three quite different mechanisms, and they fail in different ways.
- A drawn or typed markAnnotation, may not display
- An image of a signatureAnnotation or page content
- A signature form fieldForm layer, needs form support
- A digital signatureCryptographic, shows as a panel
- A flattened signaturePage content, always visible
Digital signatures are a separate matter entirely. They are cryptographic attestations about the document rather than pictures of a name, and readers display them in a status bar or signature panel rather than on the page. A recipient reporting that they cannot see a digital signature may simply be looking at the page rather than the panel.
Flattening
Flattening merges the annotation layer into the page content. After it, the signature is drawn as part of the page like any other graphic.
Finish the document completely first
Flattening is one way, so make sure nothing else needs adding or correcting before you do it.
Flatten, or print to PDF as a substitute
A dedicated flatten option is cleanest. Failing that, printing the document to PDF renders the page as displayed, which achieves the same result.
Open the output in a different reader
Ideally a browser, which is a good proxy for a simple viewer. If the signature shows there, it will show for your recipient.
When it displays but does not print
A variant worth knowing, because the cause is more specific. Some readers have a separate setting controlling whether annotations are included in printed output, and it is not always on.
In Adobe Reader this appears in the print dialog as a choice about what to print, with options covering the document alone or the document with markup. A signature on the annotation layer will not print under the first option. Flattening removes the distinction, since there is no longer an annotation to exclude.
Making the signature look right
Separately from whether it shows, image signatures often look poor, and the reason is usually the source image.
Looks deliberate
- Transparent background, so the page shows through
- PNG, which supports transparency properly
- Written in dark ink on white paper, scanned
- Cropped tightly to the signature itself
- Sized to match the signature line
Looks pasted on
- White rectangle covering the form's printed line
- JPEG, which has no transparency and adds artifacts
- Photographed at an angle with a grey cast
- Wide margins of background around it
- Stretched out of proportion to fit
Flatten the signature into the page
Once it is page content every reader draws it. The file stays on your device.
Common questions
Making sure it travels.
01Why can the recipient not see my signature?
It was almost certainly added as an annotation, a layer above the page, and their reader is not drawing that layer. Flattening the document turns the signature into ordinary page content, after which every reader displays it.
02What does flattening do to a signature?
It merges the annotation into the page content, so the signature becomes part of the document rather than a separate object sitting on top. It can no longer be moved, deleted or skipped by a reader.
03My signature shows on screen but does not print. Why?
Some readers have a separate print setting controlling whether annotations are included in output. Choose the option that prints the document with markup, or flatten the file so there is no annotation to exclude.
04Should I flatten a digitally signed PDF?
No. Flattening modifies the file, which invalidates a cryptographic signature by design. Flattening applies to drawn or image signatures, which are pictures rather than cryptographic attestations.
05Why does my signature have a white box around it?
The image has an opaque background, usually because it is a JPEG or a photograph of paper. Use a PNG with a transparent background so the page and any printed signature line show through.
06Is an image signature legally valid?
That depends entirely on jurisdiction and context, and it is not a technical question. Many everyday agreements accept them, while some documents require a qualified digital signature or a witnessed wet signature. Check the requirement for the specific document.