Thanks for your interest in Aspose.Slides.
I like to share that there are no specific JVM settings for Aspose.Slides. The OutOfMemory exception arise when your heap size is smaller then what is required. The heap size requirement varies from presentation to presentation. The presentation is needed to be loaded in Document Object Model (DOM) of Aspose.Slides and it depends on size of presentation, number of slides and contents inside the presentation. Additionally, when you export presentation to PDF it is also loaded in memory till the time it is saved in PDF. So, you need to increase java heap size on your end to avoid the OutOfMemory exception issue.