Why create one? _ "Re_inventing the wheel", is no fun. If you work for a single organisation it's likely that your templates could last a long, long time with no need to go back to the design board every time you are asked to create a new manual or user guide. When you work for yourself it's a great way to show clients that you have the skills they are looking for without breaking any confidentiality clauses with your existing clients, and with just a little bit of luck they'll adopt your method of working so you can continue to recycle your past efforts too.
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.