We have been getting questions about how the student are to send or attach assignments for grading through canvas and what do they do. There is no instruction with in assignment page on how to do that.
I would suggest that when publishing the assignment to the module to make sure that the settings for uploading attachment has the options to attach google doc. That way it can easily be uploaded to the assignment page.
This is how the assignment page should look when you need to upload from google doc
File Uploads: Students can upload a file to fulfill the assignment. DocViewer annotations are available for supported file types in Speed Grader. Additionally, if your institution has enabled Google Docs, the Google Apps LTI, or the Microsoft Office 365 LTI, students can upload files from their respective Google Drive or OneDrive account directly. If only Google Docs are enabled for your institution, students must connect to Google Docs as a web service to submit an assignment as a Google Doc, Google Sheet, or Google Slide. File upload submissions can be downloaded and re-uploaded to the Gradebook. Canvas supports file uploads up to 5 GB.
Assignment settings are persistent to always remember and display the settings created or edited in the previous assignment in the course. Based on prior assignments, one or more of these options may already be selected for you.
Note: If your institution has enabled the Microsoft Office 365 LTI, you must select either the File Uploads option or both the Website URL and File Uploads options to use the Office 365 tab on the assignment submission page. If you only select Website URL as an entry option, the Office 365 tab will not function properly.
If you allow file uploads, you can choose to restrict submissions to specific file types. To enable this option, click the Restrict Upload File Types checkbox . In the Allowed File Extensions field , enter a list of accepted extensions. All file types need to be separated by a comma. You can include spaces, caps, and periods in assignment file names.
Note: In the case of an odd or unusual file type, try adding it to your course to confirm the file is accepted before requesting students to submit the file type.
To save the assignment and publish it, click the Save & Publish button . To save the assignment as a draft, click the Save button .