How can I translate the upload form text?

Most of the app texts are already translated into multiple languages, you can edit them directly in the app:  Multi language store translations

You can also store your own translations in the app and reference them in your upload field configurations. 

Translation setup

In the app, navigate to the "Settings" tab. In the "Language settings" section, click on "Edit translations":

Here you can add your own translations. Each translation entry requires a unique key that can be referenced in the upload config:

You can change the language and enter all the texts for your translations:

Config setup

On your upload config you can then use the key defined in the translation. 
The key has to be prefix with a "#", this tells the app to replace it with the translated text.   

You can also use translations in the custom inputs, however only the label field can be translated: