Weekly PDF compression: track size and readability

For recurring PDF compression, record the source size, output size, method, and any quality setting. Each week, inspect representative text, graphics, and image-heavy pages at the same zoom in the same viewer. Check that links and selectable text remain usable. A new source may compress differently from last week's even with the same settings. Preserve originals and flag files whose size barely improves or whose critical details visibly degrade.