Monday, 19 April 2010

Embed signature (or any image) in a PDF

Today I had to embed my signature in a PDF document (a form) it. Typically, I would have printed the document, filled in the form with my signature, and scanned it back. But, I didn't have a printer or a scanner handy. I was not happy with the quality of scan available at nearby Internet cafe. So, I decided to use my digital cam to create the document.

Following is the step by step process describing the method I used to insert the signature into PDF. Hope someone else would also find it useful.

Step 1: import PDF into GIMP. Just drag and drop the PDF, the import dialog will appear. My default resolution was 100 pixels/inch. I increased it to 300 pixels/inch.

Step 2: Fill in the text using regular text tool from toolbox.

Step 3: Sign on a clear piece of white paper. Use your camera to take a picture of your signature. Open the picture in Gimp.

Step 4: In this step, we are going to remove the white background in your signature.
  • Add Alpha channel to the background layer. This enables transparency.
  • Use the "Select by color" tool (shortcut key - Shift+O). Ensure "Feathered edges" option is selected.
  • Click on the background colour to select it. Ensure all background areas are selected. You can press down shift key and add to selection.
  • Use Ctrl-X to remove the selected area. Press Ctrl-I to invert the selection. Now you should see only your signature selected.
  • To enhance my signature, I used the airbrush tool to darken the signature. This is optional.
  • Resize your image to required dimension. You could find out the required dimension by just selecting area where signature would go in and reading the dimension from status bar.
Step 5:  Copy your signature and paste it on the document.

Step 6. You are all done. Just ensure all the layers are positioned as you want. Merge and save.


  1. Its always easy to follow the step by step procedure as you have also given the steps to embed signature in pdf document without spending efforts on scanner and also maintaining the quality of document.That really sounds promising.Thanks

  2. For a multi-page pdf file, when importing the pdf file into gimp, it seems only allow one page at a time? Does it mean that the pdf file has to be splitted into single pages, and after processing in gimp, all the single pages will be merged back to a multipage pdf file?

  3. How can I go back to pdf after I have placed the image?