Standard Security Permissions

Set the user password if you don't want people to see your PDF. If they don't have the user password, it simply won't open.

You also have some control over what people can do with your document once they have it open. The permissions associated with 128-bit security (Acrobat 5 and 6) are more precise than those associated with 40-bit security (Acrobat 3 and 4). Tables Table 1 and Table 2 list all available permissions for each security model.

Table 1. Permissions available under 40-bit security

To allow readers to . . .	Apply this pdftk permission
Print—pages are top quality	Printing
Modify page or document contents,insert or remove pages, rotate pages or add bookmarks	ModifyContents
Copy text and graphics from pages, extract text and graphics data for use by accessibility devices	CopyContents
Change or add annotations or fill form fields with data	ModifyAnnotations
Reconfigure or add form fields	ModifyContents and ModifyAnnotations
All of the above	AllFeatures

2. Permissions available under 128-bit security

To allow readers to . . .	Apply this pdftk permission
Print—pages are top quality	Printing
Print—pages are of lower quality	DegradedPrinting
Modify page or document contents, insert or remove pages, rotate pages or add bookmarks	ModifyContents
Insert or remove pages, rotate pages or add bookmarks	Assembly
Copy text and graphics from pages	CopyContents
Extract text and graphics data for use by accessibility devices	ScreenReaders
Change or add annotations or fill form fields with data	ModifyAnnotations
Fill form fields with data	FillIn
Reconfigure or add form fields	ModifyContents and ModifyAnnotations
All of the above, and top-quality printing	AllFeatures

Comparing these two tables, you can see that Assembly is a weaker version ofModifyContents and FillIn is a weaker version of ModifyAnnotations.

DegradedPrinting sends pages to the printer as rasterized images, whereas Printing sends pages as PostScript. A PostScript stream can be intercepted and turned back into (unsecured) PDF, so the Printing permission is a security risk. However, DegradedPrinting reduces the clarity of printed pages, so you should test your document to make sure DegradedPrinting yields acceptable, printed pages.

After setting these permissions and/or a user password, changing them requires the owner password, if it is set.