In WPS, you can add comments to the contents of PDF files, but you can't add audio comments. PDF annotations can include annotations, text annotations and shape annotations, but not audio annotations. The full name of PDF is PortableDocumentFormat, which is a file format created by AdobeSystems. It can be cross-platform, consistent in format and easy to print and share. PDF files can contain text, pictures, tables, graphics and other types of content, with high readability and ease of use, and are widely used in document archiving, e-books, online forms, e-commerce and other fields.