As for the signature of the document itself, it can be achieved by the following steps:
1. Make sure that the current document has been saved;
2. Click "Office Button";
3. Select "Prepare-Add Digital Signature";
4. If you see a phone box warning that it is best to use a third-party digital signature service, click OK;
5. In the "Get Digital ID" window that pops up, select "Create your own digital ID";
6. Enter your own relevant information in the "Create Digital ID" window;
7. In the next window, enter the purpose of adding digital signature;
8. Click OK.
I assume that you are using Word2007. If you were born in 2003, you can refer to the introduction of this webpage:/Excel/Excel/HP 0524 95572052.aspx.
Although it is about Excel, Word is also applicable.