Do you mean to the LDAP server's filesystem, or within the LDAP servers
directory (directory in this context meaning the LDAP servers data store, not
the directory in which it is located in the underlying filesystem - terminology
is confusing when the same word is used for entirely different things)? You
could save the file as an object in the LDAP directory itself, if it isn't too
large.

The LDAP server allows you to search and add information into its own directory.
But there is no access to the LDAP server's underlying filesystem.

Assuming you  mean the LDAP server's underlying database, then yes, you
can can save files in it. That's how you can save jpg files in the
jpegPhoto attribute. Binary data has to be stored in binary attributes,
which in Java you would use a byte[] data type for handling that type of
data. I've never attempted to store plaintext files in an LDAP database
and that isn't what they are supposed to be used for anyway. If you have
textual data then put it in attributes because the plaintext files can't
be searched while they are in the LDAP database. They would have to be
retrieved one at a time and then searched by the client; not very
efficient to say the least.