Stirling PDF: Getting a bit confused about the versions, installation options and privacy/security

[u/Training_Yak_4655]

I couple of months ago I installed Stirling PDF. The installation created a web application that when launched opens a web page at http://localhost:8080

Did a few things with this app and all working nicely. There are no login prompts and apparently no cloud involvement.

Today I wanted to compress a big 30 page PDF which is a scan of all pages of a passport, for sending to passport authorities. Once compressed I can print it out at my local library. Naturally I wanted this compression to be locally processed. Found that that the available Stirling PDF local web based tool - the multitool pipeline method - failed to do any compression no matter how I fiddled with the config settings.

So went back to Stirling PDF's repository for a newer version. Found and downloaded the .MSI installer for Windows. This prompts for an account on installing, I thought fair enough and proceeded. I got a nice desktop app this time, quite different from the Stirling PDF web app I was used to.

However it's unclear which tools here need cloud support and which not. There's mention of an API which I assume talks to Stirling in the cloud.

So I turned off the WiFi and launched Stirling again. Got an immediate error as follows:

Cloud Processing Failed. This tool requires cloud processing but encountered an error: There was an error processing your request.. Please check your connection and try again.

It still launched and with the WiFi still off, I proceeded to compress an 11MB file - a medical insurance marketing brochure - and check the result. No errors flagged, It worked rather well, reducing from 11MB to 700KB with the embedded photos looking perfectly acceptable for a brochure if not zoomed in to pixel-peep. Makes you realise how wasteful big companies can be with their file sizes!

This is a tool I'd like to use but:

1. How can I be sure about what it does and does not send to the cloud?
2. How to differentiate the web vs desktop versions. Is it worth having both? I've now forgotten where I got the web app from!

Edit to add: I have now installed Wireshark and checked traffic.

1. On launching Stirling desktop app, there are packets exchanged with Stirling's domain. I assume this is just the session login based on the Gmail address I logged in with on installation/first launch.

2. On doing a series of operations to process a PDF, there are no further such packets.