You can import Adobe InDesign documents (IDML) into Affinity Publisher.
The importing of documents in Affinity Publisher is a one-way process. You cannot overwrite the original file once it has been imported. Imported documents must be saved as an .afpub file.
Affinity Publisher can import InDesign files that have been saved in IDML (InDesign Markup Language) format, which is available in InDesign CS4 and later. With earlier versions of InDesign, you can export documents to PDF and then import that format directly into Affinity Publisher.
The dpi (dots per inch) setting of the resulting Affinity Publisher document is decided as follows:
A document's dpi setting can be changed at any time in File>Document Setup.