PDFTron is now Apryse. Same great products, new name.
Yes, we encourage developers to use our demo version to begin their integration work, before licensing. While there may be watermarking, or a limited number of days to evaluate, there are no other functional, or non-functional, differences, so you can begin integration, and know that once you purchase a license everything will work as it did during the demo period.
While we encourage you to use our demo version for evaluation and integration, you can not use our demo version in production, or make it available to end users.