How to Sign a PDF Using PDFpen

How do I sign a PDF? If you’re asking this question, it’s because you suspect there’s a better, faster way to add your signature to documents than printing, signing, then scanning them. You’re right. In this post, we’ll show you how to quickly sign a PDF using PDFpen on your Mac or iPad/iPhone.

PDFpen helps you sign PDF documents quickly without having to print and scan.
No need for printing and scanning when you have PDFpen. Photo by Adeolu Eletu on Unsplash

Someone emailed you a document. You need to sign and send it back right away. You could set aside 10 minutes for that (assuming you haven’t run out of paper and your printer doesn’t act up) OR you could use PDFpen to add your scanned signature to it within seconds.

(Granted, if you don’t already have an image of your signature, producing one and scanning might take a few minutes. But once you save it to your computer, signing future documents will be a breeze.)

How to Sign a PDF in Seconds

The fastest way to sign a PDF is to add your scanned signature to it.

In this post on how to fill out a PDF form, we gave an overview of the steps involved in doing that:

  1. Get an image of your signature. (Scan it, take a digital photo, or use a drawing program.)
  2. Add the image of your signature to the form. 
  3. Crop and resize as needed.
  4. Make the image transparent so you can place it above the horizontal line.
  5. To make adding your signature easier next time, save your transparent signature to the PDFPen Library. 

We’ll look at each step in more detail below.

Adding Your Signature

In PDFpen, there are three ways to add an image to a PDF:

Signing a PDF with PDFpen starts with adding a signature. This GIF illustrates how.
Adding an image via the Insert button. GIF by Smile/GIPHY.
  1. Click the Insert button in the toolbar. A window will open. Navigate to the image you’re looking for and click Open. The image will appear in the center of the page by default.
  2. Drag and drop your image from a folder on your computer. You can also drag and drop from Safari or iPhoto directly to the PDF page.
  3. Use the Clipboard to copy and paste an image to the PDF page. (Click on the page you want the image to appear in before pasting. If no page is selected, and the keyboard focus is on the Thumbnails in your Sidebar, the image will appear on a new page among your Thumbnails.)

Use any of the three methods above to add your signature to your PDF.

Resizing Your Signature

Signing a PDF sometimes involves resizing your signature, as this GIF shows.
Resizing a signature in PDFpen. GIF by Smile/GIPHY.
  1. Select the Edit tool (arrow).
  2. Click on the signature.
  3. Drag the selection handles to resize. Hold down the Shift key to keep the image proportional.

Cropping Your Signature

  1. Select the Edit tool (arrow).
  2. Click on the signature.
  3. Choose Edit > Crop Image.
  4. Find and drag the corner or side handles of the crop area to resize and reshape.
  5. Click on and drag your crop area around your image to move it into position.
  6. Click Crop, and the image will crop to the area specified.

For more on working with images, signatures, objects, and imprints in PDFpen, check out this page.

Making (the Background of) Your Signature Transparent

You produced an image of your signature and made it just the right size for your document. You could stop there…

… or you could take one additional step to make your electronic signature look much more professional.

The extra step is making the background of your scanned signature transparent. It takes just a few clicks and makes a world of difference. This is how you do it, as described in our Help documentation:

  1. Use the Edit tool to select your signature.
  2. Choose Edit > Make Transparent Image.
  3. In the window that opens, use the eyedropper to click on the background color of the signature. Usually, this means anywhere on the white part. The Tolerance slider can adjust how sharp the edge of the transparency appears.
  4. Click Make Transparent.
  5. If your signature appears too thin, choose Edit > Undo, and repeat Step 3 with decreased tolerance. Use resizing handles, with the Shift key held down to constrain proportions, to resize the signature to fit appropriately.

If you are new to PDF editing, the steps above might sound a little more complicated than it is, so here’s a video demonstration to prove that it’s actually simple:

Video tutorial by David Sparks/Smile

Saving Your Signature to the Library

After taking all these steps to make your signature PDF-perfect, you’ll want to save it to the Library so it’s ready for reuse in the future. Here’s how:

  1. Choose Window > Library (or Cmd+Y) to open the Library window.
  2. Using the Edit tool, select your signature on the page.
  3. Click the plus (+) button at the bottom of the Library window.
  4. Choose Add Selected Imprint.

Signing PDF Forms by Drawing a Freehand Signature

Some forms come with an interactive signature field. You’ll know when this is the case when you see an arrow with a Sign Here stamp:

Sign here stamp. Screenshot from Take Control of PDFpen, by Michael E. Cohen.

You can sign interactive fields with either your finger or a stylus. Just click the signing area to start and double-click it when you’re done.

Electronic vs Digital Signatures

Did you know? There’s a difference between an electronic and a digital signature.

“An electronic signature is a visible representation of a person’s name or mark, placed by a person on a document or in a communication, by electronic or electronic and mechanical means, to identify the person and indicate that they put their mind to adopting the document or communication,” explained head of corporate law Timothy Perry on Legal Insight.

A digital signature, he added, “is concerned with cryptographic authentication technology rather than a person signaling their assent to a document by marking it.”

For more on digital signatures, digital certificates, and ensuring the integrity and authenticity of documents, check out our blog post on this topic.

For instructions on signing a PDF with a digital signature, and creating your own digital certificate, check out this page.

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