What people ask before signing their first batch.
Not a marketing list: these are the actual questions that land in hola@fdo.app. If yours isn't here, write in and it gets answered — and if it's a common one, it gets added.
Is the signature placed by Fdo. legally valid?
What Fdo. places is a simple signature: an image of your signature on the PDF. In private and commercial contexts that is what's usually accepted — contracts between companies, quotes, internal certificates, copies for clients.
For interactions with public administrations you typically need qualified electronic signature (AutoFirma with an FNMT certificate, DNIe, or any other issued by a qualified trust service provider). Fdo. does not replace that. If in doubt, ask the recipient what level of signature they require.
What if a PDF is password-protected?
If it has an open password, Fdo. asks for it when you load the file. If it has edit restrictions but opens without a password, Fdo. tries to sign anyway; if the restriction blocks modification, you get a message and that PDF is marked as not signed in the batch.
The cleanest approach for restricted PDFs is to regenerate them without protection or ask the sender for an unrestricted copy.
Can I recover a PDF if I close the tab without downloading?
No. Fdo. works in browser memory and closing the tab releases everything. That is what makes the tool private by design, but it also means you have to finish the flow in a single session: load PDFs, set up the signature, download.
If your browser crashes, the original files on your disk are untouched, so you only have to load them again.
Does it work on mobile?
Yes, with caveats. Loading PDFs and drawing the signature with a finger work fine on modern tablets and phones. What is not great on mobile is precise placement of the signature with a finger: if it has to land exactly on a small box, a mouse gives more control.
If your batch is large, mobile memory can also be a bottleneck. Processing a hundred multi-MB PDFs is more comfortable on a computer.
Why does the signature look slightly off on some PDFs?
If you use the text-anchor mode ("Signed:", for example), the signature is placed relative to that text. If on a particular PDF the text is in a different position or has a different typeface, the anchor can land a few pixels off. The app has a review tab where you can preview every page before downloading and fix the ones that need it by hand.
If the PDFs always come from the same template, prefer absolute coordinates over text anchors: place the signature on the first PDF and it is applied identically to all of them.
Is my signature stored anywhere?
Only if you choose. The app has a "Remember signature for next time" option that saves the image in the browser's local storage (localStorage). That lives on your machine and is not sent to any server.
If you work on a shared or public computer, leave the option off. The signature is cleared when the tab closes.
What about the signed PDF's metadata?
The resulting PDF keeps the original metadata (author, creation dates, generating software). What gets added is the signature image as a PDF object and, optionally, a "modified by" entry with the signing date. If you need the metadata to contain no trace of Fdo., run the result through a metadata-cleaning tool.
Can I use it for my company without a commercial license?
Yes. Fdo. is free to use, including in commercial contexts. If your company would like a self-hosted version on its internal network, or a specific integration with a document system, write to hola@fdo.app.
What image formats work as a signature?
PNG (recommended, especially with a transparent background), JPG (fine when the signature is on a white background) and SVG. Quality matters: a signature scanned at 300 dpi on white paper looks much better than a phone photo of a notebook page.
If you don't have an image, drawing with a mouse or trackpad produces a crisp vector signature.
Have another question?
Write to hola@fdo.app. Replies usually come within the same business day.