I am attaching two files from the author's web site: one consists of the complete PASS, the other of the scoring instructions (with additional information - basically a test manual).
Although this measure is much longer than what you want, I believe the 12-item version can easily be reconstructed based on the information provided in the manual.
Section One of the scale measures the frequency of procrastination. It is 18 items long: 6 mini-sections, 3 items each. The "total score" for this section is the sum of the first two items in each section (1+2+4+5+7+8+10+11+13+14+16+17: 12 items!). This makes sense, because the third item in each section asks about the test-taker's desire to change the behavior in question. So although I'm not absolutely certain, it looks like these 12 items are the short form that is so widely used.
I suggest contacting the authors directly with any follow-up questions.