I am working on a document with about 90 pages. Try to delete the first 20 pages without disturbing text and objects on remainig pages. How can that be managed?Meet the Experts
To delete pages you may simply delete them from pages panel or by simply moving first 20 pages to new document. It will not effect text on remaining pages until the text is threaded.
For Details Click here : Manage pages and spreads in InDesign
If the text is threaded then you have to break the thread first and then delete or move pages, for details click here: Thread text among frames in Adobe InDesign .