Navigo Decouverte

You may purchase a Navigo Découvert anytime you like (5€). It should be configured with bearer’s name and photo before use.

If you load a pass, such as the Navigo Semaine or weekly pass (30€) on a Saturday, the pass will become usable on the following Monday through Sunday period.

To say it another way, yes, you can buy the pass the Saturday before the week in which you intend to use it. Your plan will work.

Thank you both!

Also recently read that if you have a smart phone, you can add - Bonjour RATP app and it can be used like the Navajo pass. I haven't personally tried it, but if you search recent posts, its in the comments on a similar posters question.

If you already have an existing Navigo Découverte Card (physical card); you can top up with a new Navigo weekly pass by using the Bonjour RATP app on your smart phone. Otherwise you will need to buy a new Navigo Découverte Card first; then load it with the weekly pass.

Note:

• If you buy pass on Monday - Thursday it's for the current week; Friday - Sunday is for the following week.
• You will need to affix a face photo (3cm x 2.5cm) and your name on the card. Without these you can get a fine by inspector.
• New card is 5€, the all-zone weekly pass is 30€ (they raised the price)

https://community.ricksteves.com/travel-forum/france/top-up-old-navigo-decouverte-card-using-bonjour-ratp-app-on-phone

And for the photo it can be one that you print out on regular paper. I had my photo taken on my iPhone, sent it to my computer, resized it to the dimensions and printed out a few copies. Then I just attached it to the Navigo-D once I got the pass.

Enjoy your trip.

I just copied our driver’s license pictures and cut them down as needed. Quick and adequate.

This is the official requirement for Navigo Découverte photos:

1.3. Pour être valable, le titulaire doit inscrire ses nom et prénom, coller sa photo (de face, tête nue, fond neutre, non utilisée, non scannée, non photocopiée) et apposer le rabat autocollant sur la Carte Nominative Transport.

https://www.iledefrance-mobilites.fr/cgvu-passe-navigo-decouverte

For a valid Navigo Découverte card, the bearer must print his name and first name, attach his photo (face only, no hats, neutral background, new, not scanned, not photocopied), and place the photo under the self-adhesive cover.

At a minimum, it should be a very good quality photo.

We arrived in Paris on Monday at Gare Montparnasse and purchased the Navigo Decouverte card (and 1 week pass) there. I brought a couple of extra passport photos with me and they worked just fine. The customer service agent just cut them to size with scissors and we were good to go. I read online that the ticket office is right next to the metro ticket machines so luckily I knew where to go. Our wait in line was only about 10 minutes and she loaded it up for a week (Mon-Sun, all zones). We have used it all week and we love it! We've already saved $ on our ticket prices and the convenience factor alone is wonderful; it takes the stress out of buying tickets on the go. We've used buses, metro and RER, sliced bread!