Adobe's InDesign software package, part of the Creative Suite of applications, includes a polygon tool that can be used to create shapes with any number of sides, including triangles. Once created, these shapes can be modified in terms of size, colour, rotation and other characteristics from the program's on-screen toolbars and panels and using the mouse. Further options and settings for the shape can be accessed via the "Object" menu.
Launch InDesign and open the document you wish to work with (or create a new one). If the toolbox is not visible select "Window" and then "Tools" to show it.
Click and hold on the "Rectangle Tool" icon in the toolbox, then select the "Polygon Tool" option from the pop-up menu.
Double-click on the "Polygon Tool" icon to bring up the settings dialog box. Choose "3" as the number of sides and click "OK" to confirm.
Click and drag out the triangle shape as required. When the shape is in place use the options on the Control toolbar to configure its colour and other characteristics (select "Window" then "Control" if the toolbar is hidden).
Use the handles at the edges of the triangle shape to adjust its size, position and rotation. Hold down the "Shift" key when resizing to maintain the current aspect ratio.
To create a right-angled triangle, drag out a rectangle shape using the Rectangle Tool, then switch to the Pen Tool and click on one of the shape's corners to collapse it into a triangle. Fill and outline colours, as well as size and rotation, can then be adjusted as described above.
The steps listed in this article apply to Adobe InDesign CS6, the latest version of the software as of April 2013. If you are running a different edition of the software the process may vary slightly.