Hi @julian1994acuna,
Do you want to download files from SharePoint library on mobile?
Could you please tell me more about your scenario?
Actually, you could directly download files from a custom library you created on your side but it is not available for a default library like Documents.
You could use the following formula to download files:
Download("https://<site URL>/_layouts/download.aspx?SourceUrl=/sites/sitename/libraryname/filename.pdf")
Or you could create a share link to download it.
Here is a thread that I have answered, you could check either of the above solutions from there.