The two images (muster roll and witness statement) have been scanned at 96 dpi.
96, or even 75, dpi is fine for viewing on a computer monitor, however, just as the o/p has found, if you try to enlarge them the quality/readability will deteriorate.
As a rule of thumb, 75-150 dpi is fine for viewing at full size on a computer screen whereas 300 is the optimum for photographic printing. If there is likely to be any need to view somthing at a larger size, you need to up these figures proportionately. Using a higher figure for printing simply wastes disk space. It is generally agreed that increasing resolution beyond 300 doesn’t give you a better image.
What we don’t know is the degree of compression. A perfectly acceptable image can be ruined by too much compression + modifying & re-saving a .jpg as a .jpg can also play havoc with quality.