File Upload field can upload a single file by default. But if you want to allow your users to upload more than one file with one input, you just simply can do it by using weForms.
Adding File Upload Field on Form Builder
Please navigate to wp-admin→ weForms→ All Forms→ edit/create a form→ add file upload field to the form builder→ field options
Personalise your settings!
Now, from the advanced field options, input the maximum file size and maximum files that you want to allow uploading from the users. Click on the ‘Save Form' after you finished.
View it from the frontend
You are all set! Now preview the page and try uploading multiple files as shown in the image below.