Create and use signatures in messages
You can create prepared text, called a “signature,” to include in your messages. For example, you could create one signature with your mobile phone number to use for friends, and another with your office phone number for work. If you use several email accounts in Mail, you can create signatures for each account.
Create a signature
Choose Mail > Preferences, then click Signatures.
In the left column, select the email account you want to use the signature for, then click the Add button
.You can drag signatures from one account to another, or to and from All Signatures. If you create a signature in All Signatures, you must drag it to an account to use it.
In the middle column, type a name for the signature.
The name appears in the Signature pop-up menu in the message header when you write a message.
In the right column (the preview), create your signature.
You can use the Edit or Format menus in Mail to change the font or layout, turn text into links, or check spelling. To add an image, drag the file into the preview.
To delete a signature, select it, then click the Remove button 
. When you delete a signature from All Signatures, it’s also deleted from accounts that use it.
If you want your signature to appear after the original text of messages you reply to or forward, deselect the “Place signature above quoted text” checkbox.
Select a default signature
If you created multiple signatures for an email account, you can choose one to automatically add to messages you send from that account.
Choose Mail > Preferences, then click Signatures.
Select an account in the left column.
Click the Choose Signature pop-up menu, then choose a signature.
To automatically alternate between the signatures, choose At Random or In Sequential Order.
Use signatures
Add a signature to a message: Click the Signature pop-up menu in the message header, then choose a signature. If an expected signature isn’t in the pop-up menu, choose Edit Signatures to open Signatures preferences, then verify the signature is in the account.
Delete a signature from a message: Select the signature, then press the Delete key.
Replace a signature in a message: Delete the existing signature, then add a different signature.
Change the default signature: Choose Mail > Preferences, click Signatures, click the Choose Signature pop-up menu, then choose None or a different signature. If you use more than one email account in Mail, make sure the intended account is selected in the left column.
Depending on how a recipient’s mail server handles signatures, your signature may appear as an attachment or image to the recipient.
If you use iCloud Drive on your Mac and other devices, your signatures are automatically updated and available on those devices. For more information, see Store your desktop and documents in iCloud.
If you need to send a signed PDF document, you can use Markup in Mail to create a handwritten signature and add it to the document. You can also use the Preview app to fill out and sign PDF forms.