esp01 modules tend to have smallish flash chips installed something with a 4meg or bigger flash is better. [wemos d1 mini or d1 mini pro]
i set the esp up as a simple web server. user can upload/download files from the server via a html script using any sort of browser.
the esp can then send or fetch the file data from the pic via a ttl serial connection or spi or i2c or whatever floats your boat at whatever speed you like
whenever you like. no special software is needed at all in your browser for most common file types to upload or download successfully

https://www.picbasic.co.uk/forum/sho...776#post154776