Check your local public library or university library. Many libraries have digital lending platforms (like OverDrive or Hoopla) where you can borrow the PDF for free legally. Also, the Internet Archive (archive.org) sometimes hosts out-of-print editions of older Assimil courses (pre-1990s) that are in the public domain depending on your country.
Each lesson typically includes:
Week 1–4 — Passive immersion
Week 5–8 — Active work
Need to find every instance of the subjunctive mood? Ctrl+F (Command+F) is your best friend. A physical index is helpful, but digital search is instant. assimil french with easepdf