dRofus Built-in Reports are developed to be able to manage large amount of data and pages in a PDF document. The reports are built to exclude non relevant data to assure speed and good performance in the report generation process.
When a third party tool is used for creating custom reports without dRofus involvement, dRofus can no longer guarantee similar speed and performance as with the built-in reports. The speed and performance will then come down to how the custom report is designed.
There is some important techniques to use when creating reports that are suppose to handle thousands of pages.
Split in several page sequences
When generating a large amount of pages it's important that the data is split up in multiple page sequences (e.g. one sequence per room) so that the report engine can generate the pages for one room and then free up it's resource before it continues to the next. In XF Designer you do this by creating a repeating page set.
Page numbering
You should avoid having forward references to later pages when creating large reports. Typically page numbering and page citations like Page X of Y and in table of contents should be avoided. The reason for this is that the report server can't finish generating page 1 until the last page in the report has been generated because it does not know how many pages there are. This has large performance and resource impacts.