Our library has a document scanner that can scan multiple pages into a single PDF document that can then be uploaded into Family Tree. This is a very quick process.
If you are scanning your document files from a flatbed scanner this will result in multiple "photo" images. To best keep the single pages together and in sequence, this can be done with PDF software. However, simply dropping the images into a Word file can also be a great option to assemble all the single pages into a single file.