>>>PS you can't amend something once it's been scanned - it'll be a .pdf once it reaches your computer
That depends upon how you scan it. If you open an image editing program (such as Photoshop or GIMP) and go to the File menu there will be an 'Acquire' or 'Import' option, listing your HP device there. Clicking on that will enable you to scan an image with far more control than the basic 'Scan' function direct from the printer. (For example, you can preview the scan and crop the area to be scanned. You can also scan in black-&-white or colour, with settings available to optimise the scan depending upon the type of document.). Once the image has been scanned you can manipulate it in the same way as any photograph. (e.g. by altering the colour balance or adding text). You can then save it as a jpeg image file (or as a PDF).
If you actually want to take the text from a document, rather than simply 'take a photograph' of it, you should start by opening an Optical Character Recognition (OCR) program and then scanning the document, via the File menu, into that. You'll then get a block of text which can be copied-&-pasted into, say, Microsoft Word.
Most 'all-in-one' printers are shipped with relevant programs for the above tasks but many people forget that they're available to use. In general, you should always open a suitable program before scanning anything, rather than simply relying on buttons on the printer (or on your monitor screen).