If you want to set the paper size of your document in Writer 2013, you can take the following steps:
Step 1 Open the Page Layout tab and click the Size icon. Open the Paper tab in the Page Setup dialogue box, shown as follows:
Figure 1 The Paper tab
Step 2 Select your preferred paper size from the Paper Size drop down list. If you want to customize the paper dimensions, use the Width and Height text box and enter the specific values.
Step 3 After finishing, click the OK button to complete the operation.