Unable to open .htm attached to pdf

For security reasons Acrobat/Reader restricts the type of files that can be launched, or even extracted from a file attachment. Reader installs with a default set of Attachment Launch permissions, but they can te changed. The settings are in the Registry at:

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Adobe\Adobe Acrobat\8.0\FeatureLockDown\cDefaultLaunchAttachmentPerms]

This lists explicit permissons for a specifies set of file extensions. If something is not on the list then it is allowed.

Acrobat distributes a tool for creating custom Reader installers. This is so that corporations can distribute the same setup to everyone in an organization. One of the things this Customizer does is to setup the initail registry settings.

As it happens, "htm" is not on the default list of blocked extensions, so your user must have had this setting either changed or initially set from a customized version of the Reader Installer.

Thom Parker
The source for PDF Scripting Info
[url=http://www.pdfScripting.com]pdfscripting.com[/url]

The Acrobat JavaScript Reference, Use it Early and Often
[url=http://www.adobe.com/devnet/acrobat/javascript.html]http://www.adobe.com/devnet/acrobat/javascript.html[/url]

Then most important JavaScript Development tool in Acrobat
[url=http://www.pdfscripting.com/public/34.cfm#JSIntro][b]The Console Window (Video tutorial)[/b][/url]
[url=http://www.acrobatusers.com/tutorials/2006/javascript_console][b]The Console Window(article)[/b][/url]

What if this registry key is absent? I did see a similar answer somewhere else but I did not see the key and was not sure it was OK to add it or not.

You could delete the key and see what happens. Reader might just reinstall the defaults, or it might crash. Don't know until you try. But I'd suggest adding or modifying the entry for "htm" so that it works.

BTW, there's another registry key that relates to this issue.
[HKEY_CURRENT_USER\Software\Adobe\Adobe Acrobat\9.0\Attachments\cUserLaunchAttachmentPerms\cAttachmentTypeToPermList]

This key is different on different systems so you might have to search for it.

Thom Parker
The source for PDF Scripting Info
[url=http://www.pdfScripting.com]pdfscripting.com[/url]

The Acrobat JavaScript Reference, Use it Early and Often
[url=http://www.adobe.com/devnet/acrobat/javascript.html]http://www.adobe.com/devnet/acrobat/javascript.html[/url]

Then most important JavaScript Development tool in Acrobat
[url=http://www.pdfscripting.com/public/34.cfm#JSIntro][b]The Console Window (Video tutorial)[/b][/url]
[url=http://www.acrobatusers.com/tutorials/2006/javascript_console][b]The Console Window(article)[/b][/url]