A letterhead is the banner at the top of a letter. The heading usually consists of a name and an address, a logo, and sometimes a background color. You can also design a letterhead in Salesforce; it will give you the same look and feel as that of an HTML e-mail template. Before you create a letterhead, you first need to have your logo in the document folder. The size should not be wider than 600 pixels, and the height should not be more than 200 pixels.
To upload your company logo in the document folder, follow these steps:
Click on the Documents tab and then click on the New button.
Enter data in Document Name and Document Unique Name will be autopopulated. Select the Externally available image checkbox and the destination folder where you want to save the image, then browse to the image and click on Save. You can see this in the following screenshot:
