Practical guide

How to scan your signature properly.

The quality of the signature image shows up clearly on the signed PDF. A phone snapshot of a notebook page gives an ugly, unprofessional result. Five minutes and the steps below get you a vector-feeling signature you can reuse for the rest of your career.

Step 1

The paper

Use a plain white sheet — no grid, no lines, no logos. A4 size is fine. Make sure it is clean: that morning coffee stain shows up on the scanned signature with the same intensity as the ink.

Plain white A4, normal weight (80 g/m²).
Pen or fineliner with dense ink. Black or dark blue is best; light blues vanish on scanning.
Sign large — about double the size you'd sign on a normal document. That lets you scale it down later without losing definition.
You can do 4 or 5 signatures on the same sheet and pick the best one.

Step 2

Capturing the image

With a scanner (best option)

If you have access to a home or office scanner, use it. Settings:

Resolution: 300 dpi minimum. 600 dpi if your signature has fine detail.
Colour mode: Colour or greyscale. Pure black-and-white loses the nuance of the stroke.
Format: PNG if the scanner allows; otherwise TIFF. Avoid JPG: the edges blur.

With a phone (quick alternative)

If you use your phone, do it well:

Natural light next to a window, no shadows from your body or the phone.
Phone parallel to the paper, not at an angle.
Camera "Document" mode (if available) — it crops and flattens.
Apps like Microsoft Lens or Adobe Scan handle this reasonably well and export PNG.

Step 3

Removing the white background

A signature on a white background looks bad on a PDF that has shading or borders. Ideally the background is transparent, leaving only the stroke visible.

Three ways to get there:

Inside Fdo. itself. When you upload the image, there is an "auto-crop white background" option. For decently scanned signatures it works 90% of the time.
In GIMP (free). Open the image, Layer → Transparency → Color to alpha, choose white, tune the threshold. Export as PNG.
In web tools. remove.bg and similar work, but they upload your signature to their server — exactly what Fdo. avoids. Prefer the local option.

Step 4

Save and verify

Save the final file as signature.png in a folder you'll find later. Before using it, open it and check:

The background is transparent (not white).
The stroke is crisp — zooming in doesn't reveal pixelated squares.
There are no stains, shadows or stray text from the sheet you signed on.
The crop leaves a small margin around the signature; it doesn't touch the edges.

Alternative: draw directly inside Fdo.

If all of this sounds like too much fuss, the app lets you draw the signature with mouse or trackpad. The result is vector — crisp at any size — and takes ten seconds. The catch is that drawing your own signature with a mouse takes a few tries to look natural.

On tablets with a stylus (iPad, Surface, Wacom), drawing the signature with the pen gives a result almost indistinguishable from a scanned signature. If you have one, that's the cleanest path.

Common mistakes

Plain phone photo. Compressed JPG, body shadows, low contrast. Use a scanner or a scanning app instead.
Signature on grid paper. The notebook lines come along with the signature. Repeat on plain paper.
Light-ink pen. Comes out pale grey on the scan, almost invisible on the PDF. Use dense-ink pen or a fineliner.
Signature too small. Scaling it up on the PDF pixelates. Sign large originally.
JPG with white background. The white shows when the PDF background isn't pure white. Convert to PNG with transparency.

Once you have it, in Fdo.

Upload the PNG the first time, tick "remember signature" if you want it available across future sessions, and from then on every batch only needs you to load the PDFs and download. The signature itself is set up once.

Try with your signature FAQ →