https://helpx.adobe.com/acrobat/using/digital-ids.html
Steps to create an Adobe Signature in Acrobat PDF.
1. In Acrobat, click the Edit menu and choose Preferences > Signatures.
2. On the right, click More for Identities & Trusted Certificates.
3. Select Digital IDs on the left, and then click the Add ID button.
4. Select the option A New Digital ID I Want To Create Now, and click Next.
5. Specify where to store the digital ID, and click Next.
New PKCS#12 Digital ID File
Stores the digital ID information in a file, which has the extension .pfx in Windows and .p12 in Mac OS. You can use the files interchangeably between operating systems. If you move a file from one operating system to another, Acrobat still recognizes it.
6. Do the following:
Type a name, email address, and other personal information for your digital ID. When you certify or sign a document, the name appears in the Signatures panel and in the Signature field.
Choose an option from the Key Algorithm menu. The 2048-bit RSA option offers more security than 1024-bit RSA, but 1024-bit RSA is more universally compatible.
From the Use Digital ID For menu , choose whether you want to use the digital ID for signatures, data encryption, or both.
Click Next.
7. Do the following:
Type a password for the digital ID file. For each keystroke, the password strength meter evaluates your password and indicates the password strength using color patterns. Reconfirm your password.
The digital ID file is stored at the default location as shown in the File Name field. If you want to save it somewhere else, click Browse and choose the location.
Click Finish.
8. The ID is created. You can export and send your certificate file to contacts who can use it to validate your signature.