Do not open email attachments, as they are one of the most common causes of innocent computer users getting infected with malicious malware. Email attachments are "the kiss of death." Ask the sender to place the attachment in Dropbox, etc. or other safer alternatives. Furthermore, Mac and Windows 10 users can open PDF files by themselves, so no need to download and install additional software like Adobe Reader. There are too many vulnerabilities these days regarding email attachments and outdated Adobe software.
If you assume you are infected with malware, the best thing to do would be to erase your hard drive and start over by reinstalling. Back up your important data in an external hard drive.