Acrobat Reader has grown from a simple portable document reader to a behemoth. Most of the time you just want to view a PDF. You don't need all the features of Acrobat when you already have a perfectly good PDF reader in Preview.app.

1. Make Preview.app your default PDF viewing application. To do this find a .PDF file and use the Get Info command. Choose Preview from the "Open with" section. Then press the "Change All…" button. The next time you open a .PDF it should open in Preview.
2. If you must use Acrobat then be sure to disable JavaScript. There's almost no reason why you need JavaScript in a PDF. If you ever do need it then you can turn it back on. Preferences : JavaScript : Enable Acrobat JavaScript : unchecked.
3. Disable the Acrobat PDFViewer Internet Plug-in. It is a good practice to know when Internet Plug-ins are enabled on your computer. Plug-ins can be in several places but the two most common folder locations are in your user profile library (~/Library/Internet Plug-Ins) and in the machine library (/Library/Internet Plug-Ins). You can use your Finder's Go menu and choose "Go to Folder…" to get to these two locations. You should get rid of plug-in you no longer need. Be on the lookout for items that are in both folders -- they should only be in one location. To get rid of a Plug-In move it to a sub-folder called "Disabled Plug-Ins". You can create it if needed. This way you can recover the plug in later if you need it. The Adobe Acrobat Plug in is not required. If removed, Safari will display PDF files using preview right in the browser. There are several installers which may install the plug-in without asking you. You may need to repeat the removal process with every update of an Adobe product. You may get a message that the installation is broken or incomplete. There are some web sites that check to see if Acrobat is installed before delivering the PDF content. In those rare cases you will have to enable the plug-in again and restart Safari.