PDF 1.4 added support for Embedded Files - objects can be embedded into any PDF, including deep nesting (e.g. a PDF can contain a PDF which contains a PDF which contains a DOCX file). Via the GoToE action, links can be created that link to embedded files inside the PDF.
PSPDFKit automatically detects and shows embedded files via the
PSPDFEmbeddedFilesViewController. It is part of the default controller group which includes outline, bookmarks and annotations and only visible if the document indeed contains embedded files.
Embedded files can be accessed both via the document
allEmbeddedFiles property or also be attached to a
PSPDFFileAnnotation object. The
PSPDFEmbeddedFile object abstracts these files and allows to copy them to disk via calling
In PDF 1.7, the term "PDF Package" was created to describe a PDF document that contains a collection dictionary:
Beginning with PDF 1.7, PDF documents may specify how a conforming reader’s user interface presents collections of file attachments, where the attachments are related in structure or content. Such a presentation is called a portable collection.
(PDF Reference 1.7, 12.3.5 Collections, Page 370ff)
PDF Packages have been further improved to become PDF Portfolios via Acrobat 9. Portfolios in most cases use a Flash-based interface which has been deprecated in PDF 2.0 and is unsupported. Adobe Flash itself does not work on mobile devices and is deprecated as a whole.
Lern more on Adobe's Help Article about PDF Packages vs. PDF Portfolios
PSPDFKit has no special support for Packages/Portfolios other than fully exposing the embedded files.