You can copyright a document quite easily since the process is free and automatic upon the creation of your document. Assuming that the document in question is eligible for copyright protection, it is protected by copyright laws as soon as you create it and put it down in writing in some form. Most written works of literature or similar creations can be protected by copyright laws, though certain documents such as recipes and any public domain works are typically not protected by copyright. Though you technically copyright a document the moment you create that document, you can also register the work in order to more easily prove your copyright if necessary.
While some people assume that a document must be registered with a government agency in order to be protected, similar to a trademark, in reality you copyright a document simply by creating it. This is true in a number of different countries that have agreed upon a set standard with regard to copyright creation and protection, including the UK and the US. When you put your ideas down on paper to create a document, or even type them into a word processing program on a computer, you copyright that document in the process. The ideas themselves are not protected by copyright, however, just a realized expression of such ideas in a tangible or viewable form.
Even though you copyright a document simply by creating it, many people prefer to register such documents with a government or private agency to ensure greater protection. This typically serves to establish a legally recognized date in which the copyright can be proven, which may be important when dealing with works that are derivative of your document. In the US, for example, you can easily copyright documents in an official capacity by simply filling out a registration form and submitting that form to the US Copyright Office, along with payment of a fee and a copy of your document.
You can register your copyright through the Internet or by submitting paper forms, though online registration is faster and less expensive. In other countries you may need to register your copyright with a private agency since not every country has an established government copyright office. Though you copyright a document simply by creating it, there are certain documents and aspects of documents that are not protected by copyright. You cannot copyright a recipe, for example, but you can copyright a set collection of recipes in a cookbook; similarly, the title of your document is not protected under copyright, though you may be able to trademark it. You also cannot copyright a document that is already part of the public domain.