IMHO, nobody should be using Adobe Reader. Ever. It's a security hole into your computer. For a decade and a half, Reader has included a "feature" to allow content from the internet to be dynamically inserted when a PDF is displayed on your computer. If a website says their PDFs work only with Adobe Reader, it's a pretty sure bet they're exploiting this security hole. It boggles the mind how anyone could have ever thought this was a good idea, but malware distributors love it.
When my daughter was fresh out of college, I remember the State of Illinois encouraged her to file her tax return online by downloading and filling out a PDF, but the PDF only worked with Adobe Reader. Turned out what it was doing was dynamically changing the form as she was filling it out, and to be able to do that it required Adobe Reader to be communicating with the State's servers. Of course, if you're filling out a webform on the State's website, people would expect that kind of behavior, so that's different. But people don't expect any random PDF they download to have that capability, and that's what Adobe Reader enables.
I once had an account with a financial investment company whose monthly statements were PDF downloads that required the use of only Adobe Reader. The PDF was merely a stub that dynamically populated the display when you opened it. An analogy I used at the time was it was as though the company didn't trust mailing a statement via US mail because somebody could come by and steal the envelope out of your mailbox before you got home, so they wanted you to leave your back door unlocked and they would send somebody by to safely deposit the statement on your kitchen table instead. Wow.
Hopefully, you can see why, from a security viewpoint, this feature is a very bad idea -- and coupling it with an older, out-of-support operating system is a Very Bad Idea.
There are other, safer PDF readers you can use. Some are even portable, meaning they don't get installed on your computer. Try a few listed on
portableapps.com, where you can download one (or more), extract to a folder on your desktop, give it a try, and if you don't like it simply delete the folder and try another. If you find one you like, you can formally install a more permanent version -- or, if you're like me, you can simply move the portable folder from your desktop to somewhere else on your computer and create a shortcut to it.
My preference is Foxit Reader, though I use an old version because I absolutely detest the "ribbon" that replaced the old-style menu bar, and ribbons seem to be all the rage in everything these days. Versions after 7.0.6 are ribbon-only, but you can still find older versions on sites such as
this. (For instance, if you download Foxit Reader Portable 6.2, go to "Help > Change Toolbar Mode" to use the classic menu bar.)
You might give Foxit Reader Portable a try. If you eventually find it doesn't meet your needs, no harm done -- simply delete its folder and resume your search for something else. And if you find you absolutely must use Adobe Reader, you probably shouldn't be using Windows 7.