Metadata includes information about the document and its contents, such as the author’s name, keywords, and copyright information. To view metadata, choose File > Properties.
Files of any format can be attached to the PDF as an attachment. To view attachments, choose View > Show/Hide > Navigation Panes > Attachments.
Bookmarks are links with representational text that open specific pages in the PDF. To view bookmarks, choose View > Show/Hide > Navigation Panes > Bookmarks.
Comments And Markups
This item includes all comments that were added to the PDF using the comment and markup tool, including files attached as comments. To view comments, choose Tools > Comments.
This item includes Form Fields (including Signature fields), and all Actions and calculations associated with form fields. If you remove this item, all form fields are flattened and can no longer be filled out, edited, or signed.
This item indicates text in the PDF that is either transparent, covered up by other content, or the same color as the background.
PDFs can contain multiple layers that can be shown or hidden. Removing hidden layers removes these layers from the PDF and flattens remaining layers into a single layer. To view layers, choose View > Show/Hide > Navigation Panes > Layers.
Embedded Search Index
An embedded search index speeds up searches in the PDF file. To determine if the PDF contains a search index, choose Tools > Index and then click Manage Embedded Index in the secondary toolbar. Removing indexes decreases file size but increases search time for the PDF.
Deleted Or Cropped Content
PDFs sometimes retain content that has been removed and no longer visible, such as cropped or deleted pages, or deleted images.
This item includes objects that overlap one another. The objects can be images (composed of pixels), vector graphics (composed of paths), gradients, or patterns.