Why you should preview a PDF before signing it

Signing commits you to what the document says. But some PDFs don't always say the same thing. A script can change text when the file opens, a layer can be shown in one reader and hidden in another, an automatic action can do something you never saw. Preview the document for signing in PDF by Zaweba is there so you know what you're putting your name to.

What the preview lists

Before signing, the preview lists dynamic content in the document: scripts, XFA, automatic actions, media and layers. Each is a way a PDF can look or behave differently from one moment, or one reader, to the next.

Scripts are small programs inside the PDF. XFA is an older way of building forms whose look is generated by the reader. Automatic actions run when something happens, such as opening the file or turning a page. Media is sound or video. Layers are parts of the page that can be switched on and off.

None of these is bad in itself. A form with a script that adds up a total is perfectly ordinary. But when you sign, it's worth knowing they are there.

What you see is what you sign

PDF by Zaweba never runs scripts or media. It shows the static document: the pages as they are written in the file. So when you preview for signing, you're looking at the document itself, not at something a script has rearranged on the way to the screen.

That's a meaningful protection. A document you sign in an app that does run scripts could, in principle, look different later in another reader. Seeing the list of dynamic content gives you the chance to ask the sender about anything unexpected before you sign, or to decline.

What to do with what you find

If the list is empty, sign with confidence.

If it shows layers, look at whether anything important sits on a layer that might be hidden. A clause that only appears when a layer is on deserves a question.

If it shows scripts or automatic actions in a document that has no reason for them, such as a plain letter, ask why. In a form that does arithmetic, they may be expected.

If it shows XFA, be aware that the form may look different in other programs, and make sure what you're seeing is what the sender intends.

Exporting your certificate

The same part of the app offers Export my certificate, which saves your public certificate as a .cer or .pem file. It belongs here because it's part of signing well. Send the certificate to the people who'll receive your signed documents, and they can add it to their trusted certificates so your signatures show as valid instead of unknown. Only the public part is exported; your private key stays with you.

A signing habit

Make previewing a step you always take. Open the document, preview for signing, read the list, deal with anything that surprises you, then sign. After signing, open the signatures panel to confirm the result. It adds less than a minute.

This is one of the quieter features of PDF by Zaweba, but it reflects how the whole app works: offline, on your PC, showing documents as they are rather than running whatever might be hidden inside them.