Sign a PDF With a Photo of Your Signature (No White Box)

Sign a sheet of plain white paper with a dark pen, photograph it in even daylight, crop the photo close to the signature, then upload it in Sign PDF with Remove white background ticked. In our test that gave a clean signature with a see-through background that sat on the form’s signature line without hiding it. The things that went wrong were all in the photo: a shadow, the desk around the paper, ruled paper and pencil.

This guide is about getting the photo right. For the general signing steps and what this kind of signature is (and is not), see How to Sign a PDF Without Printing or Scanning.

Step by step

1. Sign on plain white paper (printer paper, not a notebook) with a black or dark blue ballpoint or gel pen. Sign a little larger than you normally would.
2. Take the photo in even light, ideally near a window in daytime. Hold the phone straight above the paper and make sure your hand or phone does not cast a shadow on it.
3. Crop in your phone’s photo editor so only the signature and a margin of blank paper are left. If the paper looks gray or yellow rather than white, raise the brightness or exposure until it looks white.
4. Open Sign PDF, choose your PDF, then under the signature options pick Upload and choose the photo. Leave Remove white background ticked and press Use signature.
5. Drag the signature onto the line and resize it with the corner handle. Press Apply & download.
6. Open the downloaded PDF and zoom in to 200% on the signature to check for a box, gray edges or stray lines.

Why the paper has to look white

The background removal is a brightness cut-off, not object detection. Reading the tool’s code and checking the outputs, this is what it does:

• Pixels lighter than about 200 on a 0–255 brightness scale (white or near-white paper) become fully transparent.
• Pixels between about 150 and 200 become partly see-through. Light gray paper, shadows and pale strokes fall in this range.
• Anything darker is kept as it is.
• The image is then trimmed to the part that is still visible. A desk edge or a line that survives stops the trim, so the signature ends up with extra space around it.

So the tool cannot tell paper from desk or shadow. It only removes what is close to white, which is why the photo matters more than any setting.

What we got with six photos

We signed the same one-page sample form with each photo, with the signature in the same default position and size.

Photo	Signature image in the PDF	Result	Signed PDF
A. Cropped close, daylight	832 × 208 px, trimmed	Clean: only the ink, the form shows through	101 KB
A with “Remove white background” off	1412 × 479 px	An off-white box covered the line and part of the label	514 KB
B. Whole sheet on a wooden desk	1412 × 1062 px	The paper vanished but the desk stayed and covered the form; the signature was tiny	817 KB
C. Cropped, phone shadow on the left	1412 × 479 px	A gray patch fading to white across the field	705 KB
D. Photo C after brightening	832 × 207 px, trimmed	Clean again	105 KB
E. Ruled notebook paper	1412 × 479 px	Blue lines disappeared; the red margin line stayed as a thin gray line, and the untrimmed image made the signature smaller	124 KB
F. Soft pencil	830 × 206 px, trimmed	Pale and see-through: the darkest strokes were only about 68% opaque	71 KB

The form itself was 1.9 KB. A clean, tightly cropped signature added about 100 KB. Photos the tool could not clean up added up to 815 KB, which matters if the signed PDF has to fit an upload limit.

Fixes for common problems

• A white or beige box around the signature: make a new signature with Remove white background ticked.
• A gray patch or dark corner: retake the photo in better light, or brighten it in your phone’s editor until the paper looks white. In our test, brightening the shadowed photo was enough.
• The desk, table or paper edge appears: crop the photo so only paper is left around the signature.
• Faint lines through the signature: sign on blank paper. Light blue rules disappeared in our test, but darker or colored lines (like a red margin) stay.
• The signature looks pale: sign again with a dark pen. Pencil and light gel ink come out see-through.
• The signature looks small inside its frame: something besides the ink survived (a line, a smudge, a shadow), so the image was not trimmed. Crop tighter or clean the photo.
• The form asks for a separate signature image (for example a JPG under 20 KB) instead of a signed PDF: that is a different job; see Resize an Image in KB Before Uploading.

Before you reuse your signature

• Remember on this device saves the cleaned signature image in this browser’s local storage so it is ready next time. Leave it unticked on a shared or work computer.
• Treat the original photo like any other sensitive document. Delete it from shared albums or chats once you have what you need.
• The result is a picture of your signature on the page, not a certified digital signature. If the PDF also has fillable fields, flatten it after signing so the values cannot be changed under your signature.

Limitations we found

• The background cut-off is fixed. There is no slider to adjust it, so a gray photo has to be fixed before you upload it.
• Sign PDF does not crop or rotate the uploaded photo. Do that in your phone’s editor first.
• The ink color choices apply only to drawn and typed signatures, not uploaded ones.
• Wide photos are scaled down to 1400 pixels across before processing. That was plenty for a signature, but it is another reason to crop close.
• We tested JPG photos in desktop Chrome. We did not test a real phone camera or other image formats.

How we tested this

Date	24 October 2026
Environment	Google Chrome 156 (headless) on Linux x86_64, desktop viewport 1280×900, the live tool at pdfroo.com/sign-pdf
Test files	A fictional one-page consent form (1.9 KB) with a shaded “Sign here” field, and six simulated phone photos of the fictional signature “Rina Example”, made by a script to reproduce common capture problems: five 2400 × 800 px crops (daylight, shadow, shadow brightened, ruled paper, pencil) and one 4032 × 3024 px whole-sheet photo on a desk. The daylight photo was used twice, with background removal on and off.
Settings	Upload tab, “Remove white background” on (off for one run), default position and size
Results	See the table above. Every output had 1 page and 1 embedded signature image with a transparency channel; the form text was unchanged.
Timing	Preparing the signature took 0.12–0.26 s and saving the signed PDF 0.1–0.4 s
Network	After the files were chosen, the only requests were GETs for PDFroo’s own scripts (the PDF viewer and tool code). No request went to another site and no request sent data, so neither the PDF nor the photo was uploaded.

We extracted the signature image from every downloaded PDF with pypdf, measured its size and transparency, rendered each page with pdftoppm and checked the text with pdftotext. See our tool testing methodology.

Check before you send

• At 200% zoom there is no box, gray edge or stray line around the signature.
• The signature sits on the right line and on the right page.
• The signed file is within any size limit you were given.
• “Remember on this device” is off if this is not your computer.