What do you mean by "without accessing CoH's website"? Do you mean "without navigating to CH Beta", or "without navigating to WebCheck", or something else?
If you mean:
"can I use this API (not CH Beta site) to download a copy (e.g. PDF) of a certificate of incorporation for a company?"
...then the answer is yes indeed. The documents API is what you'll need. For how to find the appropriate document ID you'll probably want to search the Filing History for your chosen company (the Filing History request). You can provide a "category" parameter which would be "incorporation" in this case.
If that's not what you meant then what did you want to do (broadest description to avoid any X-Y problems...)?
If you are using the Filing History and Documents API as per the overview above there are some more or less obscure catches as always. A short list, some / all of which you may not need to worry about:
- You may get back more than one filing entry for incorporation of course...
- Certain types of company records may not have these, or don't have any filing history at all (e.g. Royal Charter Companies, Companies where data is held by by e.g. Financial Services Register etc.)
- Incorporation should mostly be marked correctly but I've found a few where the "category" of the filing is not what would be expected e.g. filings under "miscellaneous" category, or e.g. name changes marked as resolutions with information listed in the "resolution" member of the returned data. If that might be an issue for you then you'll maybe need to start checking the descriptions etc. For a (long) list see the filing history constants.
- For downloading the file there are various quirks not noted (when last I looked) in the documentation. If you have a specific problem with that searching this site may help!
Another couple of ways to get company information via your software (these are sort of outside the scope of this forum):
1) Sign up for the Companies House XML gateway service which will charge for any downloads.
2) The company URI mechanism will give basic company data but this won't give you any documents. You can specify the data format (html, json, xml, csv etc.) Example of what you get: http://data.companieshouse.gov.uk/doc/company/00445790