How to batch download and upload files?

Hello, have you seen this blog? There are several methods in it that play with documents, download them to the server, compress them and download them to the user.

aras.com/.../download-multiple-files

I have looked at that and it is somewhat close to what I am looking for. 
I need to convert these files and upload them.
Files from multiple Documents have to be downloaded; the code only for user selecting multiple files from one Document container. I guess I could modify the above code to achieve this 

However, the files have to be uploaded once they are converted. 
How do I upload them so that they go in the right place? 

I have looked at that and it is somewhat close to what I am looking for. 
I need to convert these files and upload them.
Files from multiple Documents have to be downloaded; the code only for user selecting multiple files from one Document container. I guess I could modify the above code to achieve this 

However, the files have to be uploaded once they are converted. 
How do I upload them so that they go in the right place? 

The download multiple files project mentioned by Meupe ARAS is the perfect start for downloading the files to the server. Proven concept.

For PDF conversion get yourself a library that can do the conversion.
For uploading the files you can use attachPhysicalFile function, e.g. look for something like this Uploading Files or  https://github.com/AngelaIp/add-ssrs-reports-to-vault/blob/master/AIP_get_SSRS_Report.cs

You first have to upload the file to the vault and then link it to your item. And then you clean up everything. 

If you want to do something more fancy: Use the Aras Conversion Server do the file operation and conversion as background task. You can even use the inbuilt Aras PDF converter if you have a subscription. This is a preferred option for long running tasks were you don´t want users to "wait" for something to be finished. But it´s of course much more work :).