You can use Boxoft Screen OCR to capture Spanish sentences from protected PDF. it enables you capture anywhere on your screen, recognize every character then save as TXT file, including placement that you can't copy with mouse, such as image, dialog box and error message, etc.
Follow easy steps below:
Launch it by double click its desktop icon;
Select a kind of language which you want to extract;
Set a hotkey to later cut anywhere from PDF out conveniently;
Click "Capture" or use "Hotkey" to select words from PDF;
Click "OCR", then edit text in the popup edit box;