Sign your signature on a blank piece of copy paper. Make sure the signature is heavy and dark. Using a fine point Sharpie works well.
Scan your signature to your email. Use the highest DPI your scanner can use. This will give you a crisp signature.
Open the scanned PDF in Acrobat
Export the PDF as a .PNG file.
Open the new .PNG file in MacOS preview. Select Markup.
Use the Rectangular selection tool to box around your signature.
Then Select Crop
Upload your new signature file to https://www.remove.bg/
This will remove the background from your signature so there is no white border around it.
Download a copy with the background removed.
In Adobe, go to all tools and select add stamp.
Click on custom stamps and choose create.
Browse for the .png file you downloaded without the background. Then select OK
Create a new category named Signatures and name the signature you are uploading to correspond with the name of the signature.
To add a stamp signature just select add a stamp, and choose stamp>Signatures>and the signature you need.
The stamps come in very large. You will need to shrink the size of the stamp and place it in the correct spots in your PDF.