For many purposes you may need to create documents in applications that will then be used as templates. Sometimes applications such as Pages will provide options to save templates in a library of sorts that can be accessed when creating a new document, but many applications do not have this feature. One of the long-standing features of the Mac OS has been support for Stationery Pads, which is a way to create templates out of practically any document using the Finder.
The concept of stationery pads is relatively simple: instead of opening a document directly for editing, make a copy to open as a "new" file in the corresponding application, using the same saved layouts, settings, and other data that is stored in the stationery pad. This is exceptionally useful, because it allows you to make a template out of practically any document for use in any application, even if that application does not have options for its own template library.
To make a document into a stationery pad, just follow these steps:
Create and save a document in any application (ie, TextEdit).
Get information on the document.
Locate and check the option that says "Stationery pad" in the "General" section of the information window.
You're done. Just close the information window and the document will now be a stationery pad.
After you have done this, there is nothing special about the document. The only difference is the Finder will create a copy and open that one for editing instead of the original. Keep in mind that this feature is only applicable if you handle the documents through the Finder (ie, double-clicking). If you use the application's Open dialogue box to access the stationery pad file, it will not be copied and you will be editing the original document.