You cannot do this without additional technology. "Read" means "read into
the computer's local memory." Once there, the local user of that machine can
pretty much do anything they want with it, including selecting "Save as"
from the File menu and saving a copy on the local hard drive.
Windows Rights Management Services can help here. The creator of a document
can grant certain users (or everyone) "read-only" rights. When an authorized
user opens the document, the application enforces the rights and disables
all save, copy, export, and print functions.
Of course, RMS requires setting up an infrastructure and purchasing client
CALs. It also requires using applications that are rights-aware.
Rights-protected documents are encrypted when living on storage (either
network or local). Only right-aware applications are capable of obtaining
the decryption keys, rendering the decrypted contents in the window, and
enforcing the restrictions on the document.