Filter hook wpdm_download_link
and download_link
works differently.
wpdm_download_link
accept 2 parameters 1st parameter is download link html code, 2nd parameter is an array just contaiting package ID, ['ID' ► {Package ID}]
, and inside the filter to can retrieve package date using the give ID, $packageObject = WPDM()->package->init($param2['ID']);
and download_link
filter is documented here https://www.wpdownloadmanager.com/doc/filter-reference/download_link/
However, please let me know what are you trying to do, so that I can explain your better :).