Thanks Tim
per HMRC Website
New issues (last reviewed 05 January 2012)
Problems viewing and printing Adobe return files
We are aware that customers are unable to view or print copies of their HMRC CT600 and attachments (Version 2.3.0) and are presented with the following error message:
"This document enabled extended features in Adobe Reader. The document has been changed since it was created and use of extended features is no longer available. Please contact the author for the original version of this document"
For those customers who have already submitted their return (Version 2.3.0) and now wish to make a copy please click on the “Print” button at the top of each page to print every page as you proceed through the form.
For those customers who have saved but not submitted their return (Version 2.3.0) and don’t need to do so urgently please keep checking this page and we will inform you when a new version of the form is available to download.
For those customers who have saved but not submitted their return but need to do so urgently you will be able to use the current form (Version 2.3.0) for online filing but you will not be able to view or print the whole return in the correct format using the “View and Print” link in the product. If you wish to make a copy please click on the “Print” button at the top of each page to print every page as you proceed through the form”.
Please accept our apologies for any inconvenience caused.
Just happened to me too - HMRC are aware.
It looks like the HMRC Adobe pdf CT600 files downloaded from them before 31.12.11 all have had their extended features set to expire on 31 December 2011.
As you need these extended features for the CT600 to work, you are a bit stuffed if you try and access a CT600 downloaded before 31.12.11 after that date ie now!
One workaround is to set your system date back to 31.12.11 - this worked for me.
One would hope that HMRC have realised their cock-up and that CT600s available for downloading now have got the extended features expiry date set correctly.
See here for further details http://forums.adobe.com/thread/942994?tstart=0