I am assuming there must be some gaps in your background information / employment history so they just wanted to update all your information. however usually they do ask for only specific documents not a complete set of documents. Did you apply for EE as well? may be that file is coming up ?Here it is:
In order to prepare your application for further processing, the following documentation must be
received by our office within 30 days from the date of this letter:
For you, the principal applicant, if not yet submitted:
Offer of Employment:
If you have an offer of employment in Canada, you must submit an updated copy of the
employment offer from your employer in Canada dated this year.
Employment Reference Letter:
A letter for each declared period of employment.
Business Licence(s):
If you have declared owning equity in any business(es), you must submit a copy of the
applicable business licence(s) in addition to supporting evidence to substantiate your stated
equity
Education Credentials:
All documentation (diplomas and transcripts) to support your declared post-secondary
education or vocational training. Any foreign education credentials should be supplemented
with an Educational Credential Assessment (ECA); please see the following link for more
information: https://www.canada.ca/en/immigration-refugees-citizenship/services/immigratecanada/
express-entry/become-candidate/eligibility/education-assessed.html#designated
Language Abilities:
Any documentation you would like to submit as evidence of your abilities in either of
Canada’s official languages, English or French. You are strongly encouraged to submit the
results of an IELTS/CELPIP exam or Test d’évaluation de français (TEF).
Proof of Funds:
Any evidence of funds that will assist you in establishing in Canada.
Any other documentation you would like to submit as evidence of your ability to become
economically established in Canada.
Employment reference letter for your spouse for his/her present job. If your spouse is presently
unemployed, please submit an employment reference letter from his/her most recent employer.
For the principal applicant and all dependents, whether accompanying you to Canada or not:
If not yet submitted: Copy of the bio-data page of your valid passport.
Please DO NOT submit your original passport at this time.
For the principal applicant and all dependents 18 and over, whether accompanying you to Canada or not:
Updated Schedule A Background/Declaration Form (IMM 5669):
You must declare your personal history and addresses from the age of 18 (not only the
past 10 years). Please ensure there are no gaps in your declared personal and
residential address history.
Updated Additional Family Information form (IMM 5406)
If not yet submitted: Police certificates from each country in which you have spent 6 months or
more since the age of 18.
If you are unable to submit police certificate(s) within the 30 day deadline, submit
proof of having applied for the certificate with your package. Please be advised that all
police certificates must be provided in color.
Medical Examination: required only if you have been sent a request to update your medicals
We require proof of completion of a new Immigration medical examination. Once you have
had your medical exam, please include a copy of the receipt to our office as part of your
submission package.
For all dependent children:
If not yet submitted: Copy of their birth certificate
Try to check with the agent and see exactly which document is awaited from your side (by the application officer). The agent will confirm you if its a generic email or a case related email.