If you have Microsoft-word 2013 or later on your computer you can easily highlight your PDF file.
1- Open your Microsoft-word and Click on File;
2- Click on Open and choose your desired PDF file;
3- Click on Ok and give permission to Microsoft-word to convert your file to Doc format.
4- Now you can easily select your desired text and click on the pen to Highlight it.
5- You can easily erase the highlighted part. Select it and after that choose “No colour”, or change colour by selecting the highlighted part and choose your desired colour.
6- Click on Save as;
you can change the name of your file in filename tab, choose PDF in “save as type” part.
7- After that, you can easily open your highlighted file in Adobe-reader or Adobe-acrobat.