When a PDF 1.7-compliant viewer application initial opens a PDF document containing a collection

Beginning with PDF 1.7, PDF documents can specify how a viewer application
user interface presents collections of file attachments, where the attachments are
related in structure or content. Such a presentation is called a portable collection.
The intent of portable collections is to present, sort, and search collections of
related documents, such as e-mail archives, photo collections, and engineering bid
sets. There's no requirement that files in a collection have an implicit relationship or even a similarity; nonetheless, showing differentiating characteristics of related documents can be helpful for document navigation.
A collection dictionary specifies the viewing and organizational characteristics of
portable collections. If this dictionary is present in a PDF document, the user
interface presents the document as a portable collection. The EmbeddedFiles name
tree specifies file attachments (see Section 3.10.three, Embedded File Streams).
When a PDF 1.7-compliant viewer application first opens a PDF document
containing a collection, it ought to display the contents of the initial document, along having a list of the documents present within the EmbeddedFiles name tree.
The document list ought to contain the further document information specified by the collection schema.
The initial document could be the container PDF or among the embedded documents.
The page content within the initial document normally contains info that
helps the viewer recognize what is contained inside the collection, including a title and an introductory paragraph.
The file attachments comprising a collection are located within the EmbeddedFiles
name tree. All attachments in that tree are inside the collection; any attachments not in that tree are not. By PDF password remover, password protected pdf files can by copy or print quickly.