I am using Thunderbird 7.0.1 which comes with Vector 7.0 There is no access to PDF matters from Tools > Options > Attachments. In fact, there is no choice 'Options' under Tools.
HOWEVER, I went back to my other distro. The email client, Evolution, is where the letter containing the link to the PDF publication is found. I forwarded the email to my family account which is read by Thunderbird. The links were included in the forwarded email. I clicked on the link to the PDF publication and all I could get was a pop-up menu from Firefox reading "What should Firefox do with this file?"
Choices were: Open with [Browse] which if clicked, led me to my /home directory and also Save File. Choosing Save File places the PDF file in the Downloads folder. This then would require reading with a PDF reader, which would be fine and would solve my Thunderbird/Vector issue. All I can get by clicking on the PDF link in Thunderbird 7.0.1 is Launch Application which if I select Browse takes me to my / home directory.
So, the problem is with Thunderbird. Now, I would be satisfied if Thunderbird would even offer the option of downloading the PDF file, which would require a Browser to be activated (this, of course, does not happen)
Hope this is informative and will lead to a solution within Vector.