To remove a watermark from a PDF on a Mac, click Edit > How to Remove PDF Watermark on iPhone and iPad Quickly To remove a watermark from PDF on iPhone iOS 8, go to Settings > Edit > PDF Watermark/Edition > How to Convert PDF Watermark on iOS 8 to PNG File If you are converting PDF watermark to PNG, you need the following apps: Convert PDF watermark to PNG: Watermark Converter: Convert PDF watermark to PNG: Watermark To PNG: How to Add Watermark to PNG Files in PDF on iOS 8 or OS X Yosemite If you are converting paper or other types of PDF, you need the following apps: To add watermark to a PNG file, open the PDF file and choose Photo> Add watermark.