If you only want to track the number of counts the pdf was clicked/opened then you can simply create a ED in survey flow and set its value to 1 and then custom EOS element with redirect to pdf url.
OR
If you are putting the pdf link in some qualtrics question, then you need to add click event on anchor track and increment the ED value using JS

Thank you. That was very helpful! I like that first method.

Any suggestions on how to count the number of people, rather than the number of clicks?

At first, I thought about comparing IP addresses, counting one IP address only once. However, IP addresses are blocked by my Brand Admin.

I know that I can send a unique/personal link to each and every person but that would only allow that individual to click and view once. After that, the link becomes invalid. I would like each individual to go to the link as many times as they would like and only be counted as one response.

Thank you so much in advance.

I'm assuming you can add query strings to your URL, if yes, then you can use the ResponseID embedded data, which is for each response.

https://www.qualtrics.com/community/discussion/comment/34567#Comment_34567You can use multiple completes while distributing.