To fetch highlighted text from PDF, open PDF file on its interface, and access the Comment tab. In that tab, click on the Export option available in the Manage Comments section. You will see the Highlighted Text option. Use that option and then you can save all the highlighted text as a text file.
Once a copy has been made, just make a copy of the copied text, as highlighted in orange above, to the clipboard. Repeat all these steps with any number of highlighted words or lines, if you so desire! That's it. This will all save both space in your clipboard, and your computer's memory, which will help you to run Windows applications less often and with less strain, even on older hardware. If you do need your document saved on your computer, then just re-paste the text back over the top of the original.