PDF Permissions
When you protect your PDF documents with passwords you can
optionally specify a set of permissions. The permissions determine which kind of
access the user password will provide. Using the permissions you can prohibit
the user from printing and using cut and paste operations. See the table below
for a complete overview. The table is part of the PDF reference (third edition).
Go to www.adobe.com for a
complete reference.
| BIT POSITION |
MEANING |
| 1-2 |
Reserved; must be 0. |
| 3 |
(Revision 2) Print the document.
(Revision 3) Print the document (possibly not at the highest quality
level, depending on whether bit 12 is also set). |
| 4 |
Modify the contents of the document by operations other than
those controlled by bits 6, 9, and 11. |
| 5 |
(Revision 2) Copy or otherwise extract text and graphics from the
document, including extracting text and graphics (in support of
accessibility
to disabled users or for other purposes).
(Revision 3) Copy or otherwise extract text and graphics from the
document by operations other than that controlled by bit 10. |
| 6 |
Add or modify text annotations, fill in interactive form fields,
and,
if bit 4 is also set, create or modify interactive form fields
(including
signature fields). |
| 7-8 |
Reserved; must be 1. |
| 9 |
(Revision 3 only) Fill in existing interactive form fields
(including
signature fields), even if bit 6 is clear. |
| 10 |
(Revision 3 only) Extract text and graphics (in support of
accessibility
to disabled users or for other purposes). |
| 11 |
(Revision 3 only) Assemble the document (insert, rotate, or delete
pages and create bookmarks or thumbnail images), even if bit 4 is
clear. |
| 12 |
(Revision 3 only) Print the document to a representation from
which a faithful digital copy of the PDF content could be generated.
When this bit is clear (and bit 3 is set), printing is limited to a
lowlevel
representation of the appearance, possibly of degraded quality.
(See implementation note 16 in Appendix H.) |
| 13-32 |
(Revision 3 only) Reserved; must be 1. |
A number of the bits listed above are reserved and must be 0
whereas others must be 1. If you combine all the mandatory reserved bits you get
a decimal value of -3904. The number is negative because it is a signed
integer. With that number as a base you can add the bit values
of the permissions you want. Let's say you want the user to have print and copy
permissions then you add bit 3 for printing and bit 5 for copy. The permission
value is then -3904 + 4 + 16 = -3884.
It is important that you specify an owner password when
using this security feature. User and owner passwords must be different.
If they are the same then the user will have owner permissions, which
means that the permission settings have no effect.
You can leave the user password blank if you wish.
|
