Final answer:
To change the paper size of a document in Microsoft Word, you click on the 'Layout' or 'Page Layout' tab and then find the 'Page Setup' group to access the paper size options.
Step-by-step explanation:
To change the document's paper size in a word processing program such as Microsoft Word, you would typically click on the Layout or Page Layout tab on the Menu tab. Then, look for the Page Setup group where you will find the option to adjust the paper size.
This feature allows you to change the size of your document's pages to various standard sizes or even custom dimensions depending on your needs. It is important to note that the exact labels and placement can vary depending on the version of the word processor you are using.