PDFCACHE system variable
Enables/disables the pdf cache. A multi-resolution persistent image cache is used to display attached Pdf underlays, enabling (very) fast zoom and pan operations. The highest cached resolution is 5000 x 5000 pixels. Still, when zooming in very close, the display of the Pdf underlay will become pixelated. So a hybrid modus can be used which switches to real-time generation of crisp Pdf underlay display when zooming in very close. The initial generation of the image cache may take a few seconds, from then on processing gets (very) fast, and remains like that in subsequent sessions.
0 to 2
0: No caching, always real time generation
1: Use pdf cache, only use real time generation when zooming in close
2: Always use pdf cache