Attaching a zip file to a PDF

there are various work arounds. here is one: you can tweak the zip archive's name extension, for example, add an X like this: file_name.zipX (of course you'll need to expose the extensions in windows explorer [tools > folder options > view]). The file with 'zipX' extension will now be unrecognizable to the system and Acrobat will allow it to be attached to a pdf. The recipient of the pdf with attachment will have to drag/drop the zipX file from the attachment panel to a folder and then drag/drop the zipX file to a zip window (tested with WinZip) and then 'extract' the files. There are many variations to the process. Experiment a little. You'll need to provide instructions for your recipients.

Here's an amplification to my prior post. If your recipients use Reader 6 and earlier, they should not have a problem extracting/opening the ZIP attachment, except for some warning popups.

If they use Reader 7 and later, first they will need to make a preference setting (edit> preferences> trust manager) at PDF File Attachments place check next to "allow opening of non-PDF files ..." Now, the user will be able to extract/open many common file types, but not ZIP and others that Adobe considers to be risky.Next, you should review TechNote ID: 331371
http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=331371

This TechNote applies in particular to Reader and Acrobat 7, but it is also relevant to Readers 8 and 9. For 8 & 9 you'll find the key to be modified (tBuiltInPermList) is in the path:
HKEY_LOCAL_MACHINE\software\policies\adobe\acrobat reader\[version]\FeatureLockDown\cDefaultLaunchAttachmentPerms

The rub is that the user will have to make the modifications to the registry.

Perhaps the suggestion in my prior post that one can tweak the ZIP file extension is the way to go.