How do I set the paper size for Prism files?

Default page size

Prism always defaults to US Letter page size (8.5 x 11 inches). 

Prism 5 and earlier obtained the page size from the default printer as set in the Control Panel/Printers (Windows), or  System Preferences/Printers (Mac). This required that Prism "talk" to the printer on startup, which caused many problems, so with Prism 6 we stopped having Prism "talk" to the printer until it is time to print. If you never print, Prism never talks to the printer -- avoiding lots of issues.

Changing the page size for a project file

You can set the page size for a particular file. Drop Prism's File menu and choose Printer Setup (Windows) or Page Setup (Mac).  This choice will apply to all sheets in the file. For data and results tables, you'll only notice the page size if you print. For graphs and layouts, you'll see the page size reflected in the working area you see on screen. Use View..Rulers to make this clear. 

While the page size can be only set once per project, the page orientiation (landscape vs. portrait) can be set individually for each graph and layout sheet (in the Change menu, not on the Page or Printer setup dialogs).

Setting a custom page size

Windows

Windows lets you define custom page sizes. You must first define the custom size in the Printer control panel. This is explained in this video (not created by GraphPad). Once you create a custom page size in the Windows control panel, you can choose it in Prism's print dialog.

Mac

From Prism, drop the File menu and choose Page Setup. Then drop down the list of paper sizes. At the bottom, find "Manage custom sizes." From here, a custom page size can be defined.

If you want to default to a different page size

If you want to default to A4 (or some other) page size, Prism doesn't give you that option. New files always default to US Letter. But there is a simple workaround.

The workaround is to clone an exisitng file rather than creating a new one. Cloning is super useful if you are analyzing and graphing a series of experiments. If each project you work on is very different, It wouldn't make sense to clone a graph. Instead, make a very small Prism file and set the page size appropriately. If you delete all sheets, Prism will lose track of the page size. But you can delete all but one sheet (say a data table). Open that file, and add to it as you normally would. The page size will come from the file you opened, which can be differerent than the Prism default. Read about cloning and Prism templates.