Hi Anders,
Perhaps you are not aware this is a community application. That means that a member of the community has gone to the effort to not only learn the language, the Homey SDK but then to spend the time making the application that they created for themselves available to the rest of the community. All of which, at their own expense of time and effort.
If you would like this app to take a CSV ( a very common file, which can be used to create spread sheets, charts, import and export) in convert it to a PDF you can perhaps look at implementing it yourself and then sharing it with us?
The existing apps code can be found here.
You can read up on how to create a Homey app here.
Given that you need access to other apps flows, you will also need to know about how to use the webAPI code which you can read about here.
There are some useful tools when yousing the WebAPI documentation, they can be found here.
I found this library which is used to convert time tracking CSV into a PDF, im sure you can edit the code to work with an app, here. Also here is the actual code..
We also have a very active developers slack channel who are a great source of knowledge.
I am closing this thread, if you require any help with this app, please do so where @Gruijter has gracefully asked for more detail so he can help you out here.
