Hi MUUKOW and welcome to Bleeping Computer.
You may just have to update your Adobe Acrobat Reader.
It can be an annoying program, I don't care for it much myself.
Most often, computers come installed with Adobe which is used
to download and open PDF files.
If you have a Windows 98 or Windows ME computer, you will
find it probably came with version 4.0 or so. A download of
the latest version of 7.0 may solve your problem.
You can find that here.
Let me know if this helps.