You can configure the add-on to include multiple attachments. The add-on can add files only from Google Drive, and automatically converts Google Documents, Spreadsheets and Slides to PDF files when those files are being attached.
You can configure attachment names - attachment names will be the same as the names of files in Google Drive. You can choose a column with attachment names or you can set a name.
Be very careful when setting attachment names, whether manually or from a column. Always make sure the file type of the file being attached and the attachment name extension match. Otherwise you might attach files with wrong extensions, leaving users unable to open the attached files!
KEEP IN MIND: Certain file types cannot be attached as they might carry harmful content.