1) Go to Documents > Files > File Cabinet.
2) On the File Cabinet page, click the name of the folder where you want to store files.
3) Click Advanced Add to add multiple files.
a. Verify the Destination Folder is where you intend to upload files.
b. Check the Unzip files box to automatically extract files into the Destination folder as they are uploaded.
c. (Optional) Check the Make all Files Available Without Login box. For files that are not inteded to be published on your web site, clear this box. However, check this box to make files available for viewing in your Web site and in the Customer, Vendor or Partner Centers. All files in the Images folder and the Web Site Hosting Files folder have this box checked by default. This prevents broken images and links in your Web site.
d. Check the Overwrite Files with Same Name box to avoid uploading duplicate files in this folder. Files of the same name are automatically updated with the latest version you upload in this folder of the file cabinet. You can upload duplicate files in different folders.
So what this does is, you can upload all your files from your desktop , via a ZIP file, Netsuite unzips it and attaches to the folder. And then you can come back to your transaction, and attach the files one by one.