Designer lets you use as many pages as you need for your documents. Individual pages in a document can be of different sizes and orientations (portrait, landscape). Each page can be set up differently if needed.
You can use the Page Manager Tool to select any number of pages in your document and set them up with the same size, orientation, margins, page fill, and so forth.
If you want to remove an object from a page temporarily, you can drag it off of the page onto the working area. The object remains there until you need it again. However, if you select another page, it is not visible.