Normal procedure would be to upload the file(s) to the server, then add the location/file names to the database.
Basically:
user uploads pdf1.pdf and pdf2.pdf
files are stored in
/server/uploads/30a0afad45f674dd833c80e2edbdddc4/pdf1.pdf
/server/uploads/30a0afad45f674dd833c80e2edbdddc4/pdf2.pdf
where the hash (30a0afad45f674dd833c80e2edbdddc4) is a hash of the user
or you can store them (probably best if a user may upload files with the same name)
/server/uploads/pdf1_07ae6f4b9ce33aa04bb86680f3ab8342.pdf
/server/uploads/pdf2_585fe0da4effee4b3937d8595cc33ae1.pdf
where the hash is a hash of the actual file. so if they upload a new file with the same name it will be stored with a different file name on the server.
Then add the filename to the database.
INSERT INTO files (filename_virtual, filename_original) VALUES (‘pdf1_07ae6f4b9ce33aa04bb86680f3ab8342.pdf’, ‘pdf1.pdf’), (‘pdf2_585fe0da4effee4b3937d8595cc33ae1.pdf’, ‘pdf2.pdf’)
You might want to add user_id / owner_id and verified columns
Let us know if there is anything you need help with 