The official subscription service from Games Workshop includes a "Vault" section. They have been systematically digitizing classic White Dwarf issues, removing old advertisements and outdated rules to focus on lore and photography.
Before the discovery of the first exoplanet transiting a white dwarf (WD 1856 b), proceedings papers speculated about debris disks. Your target PDF may contain the earliest theoretical predictions for post-main-sequence planetary systems . White Dwarf 292 Pdf