Images and txt text and html files can be shown in the email by select this option: 'View' > 'Display Attachments Inline'

It is advised that you only enable that option if you are sure of the origin etc of the attachment.

All other attachments will require you to open using the appropriate program. eg: .pdf use Adobe Reader; doc/docx use Microsoft Works Word or MS Office Word or OpenOffice Writer etc

great thats what i was looking for

There is an addon which can allow viewing of pdf files:

• https://addons.thunderbird.net/en-US/thunderbird/addon/gmail-conversation-view/

It does change the view, so you may need to alter things afterwards such as viewing All folders rather than Unified.

You may discover the 'Message Pane' may look different as well.