Hello, the reason why you have watermark in your flipbook is that the software will automatic apply the last watermark settings. In other words, you have to cancel the watermark settings at first.
Here’re the steps to cancel watermark in detail:
Step1: Run Boxoft PDF to Flipbook first, then click “Set Watermark” button to enter “Select Watermark” interface.
Step2: Find the selected watermark in the list, and then cancel this option.
Step3: Click “ok” button to save settings, and re-import your PDF, then the watermark has been removed.