Is there any solution to upload multiple files directly to object?
I don’t think that directly. But in newest 5.6 version you can first upload multiple files to assets (eg via drag and drop) and in object you can have multihref (now callled many-to-many relation). In 5.6 it is then possible to select more assets (also objects, documents) and drop it into multihref at once.
Thank You @mertaivan for reply. I need more user friendly solution.
Attach PDF to DataObject
Then I can now only think of using IFrame component and built there own multifile upload solution. Or to create new data component :).