| 摘要 |
The present invention is directed to document or file access control. In particular, embodiments of the present invention alter files that are obsolete, so that it is apparent to a user that an updated version of the file should be obtained. Accordingly, files that are subject to revisions can be stored locally, to provide fast and convenient access to such files, with assurance that notice will be provided to a user if the locally stored version of a file becomes obsolete. Furthermore, the invention allows files stored locally that have become obsolete to be identified automatically. The alteration of obsolete files may include the placement of a watermark on or embedded in such files to provide an obvious indication to a user that the file is obsolete.
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