On 2013–01–23 Devendra Ghate wrote:

> >Use Adobe Acrobat and add that option to the PDF.
> >
> >Best Martin _
> Dear Martin,
> 
> Thank you for the pointer. Adobe Reader 9 (which is the latest
> version available for linux) does not allow this. However, Adobe
> Reader X (on windows) allowed comments and mark up straight away
> as no security settings are added while generation of the file.

Security settings are different from the comment ability. Security
settings *take away* permissions and can be set using a variety of
tools. The commenting ability actually *adds* a certificate which
can only be added using proprietary Adobe software, not using open
source tools. You have to purchase Adobe Acrobat.

Marco