Using the Place command, you can import pages from one InDesign document into another. You can import a page, a page range, or all of the pages in the document. The pages are imported as objects (much the same way that PDFs are imported).

Add pages in your document to hold the pages you want to import. After you choose File > Place and select an INDD file, you can choose Show Import Options and then choose which pages to import, which layers to make visible, and how to crop the imported pages. You can scroll in the Preview window to examine the thumbnail pages closely. The page or pages you select are loaded in the graphics icon. As you click to import each page, InDesign loads the graphics icon with the following page so you can import pages one after the other.