PowerPoint is actually very versatile if used correctly. It can handle anything from whiting out text boxes and speech bubbles to basic redrawing and image retouching. Like, I didn’t want to pay for expensive software for a graphic design course, so I completed it all in PowerPoint and my professor was none the wiser.
The workflow probably goes something like this: crop and rotate if necessary, sharpen image if desired, draw or drag a shape over the original text, change outline and shape color to background color, insert text box, and type translations. To save it, you could directly save the entire PowerPoint presentation as a different file type, or up you could save each page individually by selecting all the objects on the page and clicking save as image.