Hello Daniel and welcome to our forum!
The performance of report generation depends very much on how the reports are designed. For example, the contained image objects, the data source, and much more play a role here. In this knowledgebase article, you will find recommendations for optimizing the file size and speed of PDF exports. Perhaps you can apply some of the suggestions to your project.
However, in order to be able to analyze your issue in detail, please create a case via our support center.
Thank you very much!