IRCC's application forms (including the family/spousal sponsorship forms) are dynamic, fillable PDFs that only render correctly in Adobe Acrobat Reader — not in generic PDF viewers or a web browser's built-in PDF preview.
Fix:
- Download and install Adobe Acrobat Reader DC (the free version works fine; you don't need Acrobat Pro).
- After downloading the form from the IRCC website, don't open it directly from the browser — instead, right-click the downloaded file and choose 'Open with' Adobe Reader specifically.
- If your operating system automatically opens PDFs with a different default program, change your default PDF handler to Adobe Reader so future IRCC form downloads open correctly without extra steps.
If the error persists after switching to Adobe Reader, try downloading the form fresh (rather than reusing a partially-downloaded copy) and disable any browser PDF-preview extensions that might intercept the file.