From Adobe (ftp.adobe.com):
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SYSTEM REQUIREMENTS FOR ACROBAT READER
======================================

WINDOWS:
- 386- or 486-based personal computer (486 recommended)
- Microsoft Windows 3.1 or greater
- 4 MB system RAM
- 2 MB hard disk space


MACINTOSH:
- 68020- or greater Macintosh
- MacOS 7.0 or greater
- 2 MB application RAM
- 1.5 MB hard disk space


DOS:
- 386- or 486-based personal computer (486 recommended)
- DOS 3.3 or greater
- 2 MB application RAM (4 MB recommended)
- 5 MB hard disk space


DISTRIBUTING THE ACROBAT READERS
================================

Details on the terms of use for the Acrobat Reader products are
found in the Adobe Systems Incorporated Electronic End User License
Agreement that is installed with each product.


YOU MAY REDISTRIBUTE ACROBAT READER 2.0.
IF YOU WISH TO REDISTRIBUTE ACROBAT READER 1.0,
YOU MUST SIGN A LICENSE WITH ADOBE.


TO DISTRIBUTE ACROBAT READER 2.0:
You may make unlimited copies of the Acrobat Reader 2.0 software
(for Macintosh or Windows platforms) and give copies to other persons
or entities as long as the copies contain the Electronic End User
License Agreement and the same copyright and other proprietary
notices that appear on or in the Software. Because all of this is
built into the installer, you can't not do this.


TO DISTRIBUTE ACROBAT READER 1.0:
If you wish to give copies of Acrobat Reader 1.0 software (for DOS
and UNIX pltforms) to others, you must sign a license with Adobe
Systems and agree to report quarterly the number of copies you 
distribute. There is no fee. To receive a license application, call
Adobe at 1-800-521-1976.


Adobe, Acrobat, and Adobe Type Manager are trademarks of Adobe Systems 
Incorporated and may be registered in certain jurisdictions.
(c) Copyright 1994 Adobe Systems Incorporated. All rights reserved.