This means all the communications and documents submitted, generated, exchanged and issued during the international phase (PCT) and all the communications and documents submitted, generated, exchanged and issued during the different national phases for a patent between all the stakeholders, Iincluding all the notificationd to and from IPO, national patent offices, inventors, lawyers, IP agents, etc.
For the first part of the question, namely the international phase, you have most of the communications available at PatentScope, tab 'Documents' once you are in the file of a particular PCT. Documents relating to PCT Chapter II only become available after the IPRP has been issued, in the meantime it is not publicly available. And once it becomes publicly available, it is not even completely available at PatentScope. You have to find all the exchanged communications directly in the public Register of the IPEA, which may or may not make those documents publicly available. The EPO publishes them in the European Patent Register for example.
For the second part of the question, namely the national/regional phases, you have to retrieve those documents from the Register of the concerned Patent Office. I mentioned the European Patent Register already, you have the Public Pair for USPTO files, and there are many more, you can find links for the registers in the webpages of the Patent Offices. For the IP5 Patent Offices (USPTO, EPO, Chinese Patent Office, Japanese Patent Office and South-Korean Patent Office), you can also retrieve the documents through the Global Dossier, which is also accessible through Espacenet: once you are in the 'Bibliographic data' of a particular application, at the top there is a link to the Global Dossier.