Add files (pdf, txt, docx) to the left column. Type key words in the right column. Click (Search words) button. In the dialog window choose where to save the file (*.txt). The file will contain the key words plus two lines before and two lines after them, from all the files added.
Modules which are used: PyQt5, docx2txt, pdfminer3k. All of them must be installed, you can get them using pip3.