Does mdfind allow wildcard searches on filename?
This should work:

mdfind "kMDItemDisplayName == test*.pdf"


Enclose the pattern in single quotes and add 'c' to match case-insensitively:

mdfind "kMDItemDisplayName == 'test*.pdf'c"


Here is a list of available attributes. You can combine multiple attribute/value pairs with &amp;&amp;.