Hack 12 Unpack PDF Attachments (Even Without Acrobat)

Save attachments to your disk, where you can use them.

Authors sometimes supplement their documents with additional electronic resources. For example, a document that displays large tables of data might also provide the reader with a matching Excel spreadsheet to work with. PDF's file attachment feature is an open-ended mechanism for packing any electronic file into a PDF like this. As discussed in [Hack #54], these attachments can be associated with the overall document or with individual pages. You can unpack PDF attachments to your disk using Acrobat, Reader, or our pdftk [Hack #79] . After unpacking an attachment, you can view and manipulate it independently from the PDF document.

1.13.1 Unpack Attachments with Acrobat or Reader

In Acrobat/Reader 6, you can view and access all PDF attachments by selecting Document File Attachments . . . . Select the desired attachment and click Export . . . to save it to disk.

In Acrobat 5, you can view and access a document's page attachments using the Comments tab. Open this tab by selecting Window Comments. Select the attachments you desire to unpack, click the Comments button, and choose Export Selected . . . from the drop-down menu. View and access document attachments in Acrobat 5 by selecting File Document Properties Embedded Data Objects . . . .

Reader 5 and earlier versions do not enable you to unpack attachments.

1.13.2 Unpack Attachments with pdftk

pdftk simply unpacks all PDF attachments into the current directory. Future versions might introduce more control. For now, invoke it like this:

pdftk  mydoc.pdf  unpack_files

If the PDF is encrypted, you must supply a password, too:

pdftk  mydoc.pdf  input_pw  bazpass  unpack_files

Unpacking a PDF's attachments does not remove them from the PDF. You can always unpack them again later.

1.13.3 Hacking the Hack

Dispense with the command line [Hack #56] to create a quick right-click action for unpacking a PDF with pdftk on Windows.