The application that most of us use to view PDF on Mac is Adobe Reader either because of the fame that precedes him as a viewer of this type of files or because many of us are simply used to its interface, even so this does not have to be a rule, it would be missing more ... but we can consider it an option since there will be others who like more how it manages these files the Preview app already pre-installed on the system.
The problem is that when we install Adobe Reader, a plug-in is also installed in Safari that by default will act as embedded PDF viewer In the browser, let's see now how to uninstall it and have Preview as the default for these tasks again.
Actually the execution of this plugin slows down the general speed of the browser somewhat, for some it will be fine, but for others this time can be minutes of productivity so we will proceed to uninstall it.
- We will close Safari and go from the Finder to this route (press CMD + Shift + G to enter the route) and we will paste exactly this address:
/ Library / Internet Plug-ins /
- We will look for two files called "AdobePDFViewer.plugin" and "AdobePDFViewerNPAPI.plugin", and remove them. At this point we will return to relaunch Safari for the changes to take effect and we will test to see if from this moment the PDF load is performed by Preview instead of Adobe Reader.
Like we have done this for Safari, we can do it for the system in general simply by opening any PDF document with the right button> Open with and later pointing to the option "Always open with this application".

It is also no less true that lately Adobe software updates They are being fairly constant for security reasons where enough exploits have been found as a means of introducing malware into computers, so their use, even though it is practical software, is quite debatable, at least from my personal point of view.