Meta data / Custom data

Hello,

I have pdf files with link annotations. For these link annotations I want to develop a plugin, that 'evaluates' some information if the user click the annotations. But for 'evaluating', I need to store some additional informations for each link annotation. It is allowed to add metadata objects to a link annotation? For me, the pdf reference is not clear:

'Beginning with PDF 1.4, metadata can also be specified for individual components of a document.'

Or is there another possibility to add additional informations to objects?

Thanks for your help

Wolf