Function set_attachment_param 

pub fn set_attachment_param(
    edit: &mut EditDoc<'_>,
    limits: &Limits,
    index: usize,
    key: &str,
    text: &str,
) -> Result<bool, Error>

Sets a /Params text entry on attachment index’s embedded file — CreationDate, ModDate, any key — creating /Params when missing; a CheckSum given as <HEX…> is stored as that hex string. Ok(false) when the attachment has no embedded file.

Errors

When the document has no catalog to hold the tree.