Have you ever snapped photographs of your school hand-outs and compile them into a pdf file? If you've done this, you'll notice such documents are unsearchable because no reader can read texts in images but worry not because there are so mary OCR(optical Character recognition) software out there to help you read these texts in images and convert them into plain texts that are readable, searchable and editable but I've made a video showing you one of the best software out there and how to use it to make your document searchable.
To watch this video: m.youtube.com/watch?v=q90oKP2R_14&client=mv-google&gl=NG&hl=en-GB