There are some people who would prefer to have a document that is in portrait while there are some who would rather have their document in the landscape. It will depend on the type of document that you are printing. Essays, research paper, and other documents are usually in portrait form. Other documents like certificates would need to be in landscape.
There are times when you can have the same document with different document layouts. This means that some of the pages may be in landscape while the others would be in portrait form There is a section there that can be checked if you would like to do this.