The A3 paper size is one in a range of international standard page sizes, known as the A-series. A3 paper is 11.69 by 16.54 inches, or 297 by 420mm. The size is regularly used for large diagrams, tables or drawings, and also can be used to lay out a spread of two A4-sized pieces of paper. A-series paper sizes are regularly used in Europe. The alternative to A3 in America is Tabloid, which measures 11 by 17 inches. As long as you have A3 paper and a printer that will print it, you can set up any document to print on A3 paper.
Connect the printer to your computer and load the paper tray with A3 paper. If the printer has more than one tray, as is the case for office laser printers, make sure to load the A3 paper into the correct tray.
Open a document on your computer that you want to print. Change the page size to A3 so the printable area is as large as the paper is. You don't have to do this, but if the page size is smaller than the paper size, the content will not take up the whole page. For instance, in Microsoft Word, click the "Page Layout" tab, then click "Size" to select "A3." In other programs, look for "Properties" or "Document Setup" under the "File" menu to change the page size.
Choose the "Print" command to change the paper size to A3. All programs will bring up a "Print" dialogue box that allows you to customise print options. Select your installed printer that you're going to use from the drop-down menu. Click "Properties" or "Preferences." You may need to then choose "Options" or "Advanced" to access the paper size options. In the "Paper Size" menu, choose "A3". Press "OK" to return to the "Print" dialogue box.
Choose any additional printing options, such as the page range and number of copies. Click "Print" and wait while your document prints on the A3 paper.