Now, you have thousands of free document templates that can be turned into web forms. What you need is, open MS word. Then you will need to go to your title bar and move to file. Here you have several existing templates to choose from. You can choose anyone among them and modify them according to your needs. Apart from changing the forms, you can start with a scrap or, blank template.
Personally I like to place my business address at the bottom of the page or the footer. To do this go to the floating bar and click on the button, 'Switch Between Header and Footer.' This will open a dotted box at the bottom of the document. You can type your office address here or anything you see fit for your letterhead. Again you can format the text by choosing the font, font size, color, align the text, etc.