Food, Clothing, Shelter, Basic Medical Care, Education, Pension.

The first three are well known but the last three are just as true and just as critical if you wish to control population. Large families are formed to ensure pensions in your old age and to potentially cover medical costs and finally as a collective to potentially allow one of the members to be educated.

I could write forever about how to solve these problems but I'll try and give a brief review of each.

Food intensive agricultural methods coupled with drip irrigation can provide enough food
in addition land is often poorly distributed. I'm not saying you should bust up the larger farms by force but you can support smaller farmers in buying more land potentially via collectives. If you think about it for a bit formation of collectives of various sorts makes many of these problems solvable.

Clothing is not a real issue these days.

Shelter can be greatly improved with some engineering work and small factories to convert scrap materials to decent building materials. Probably one of the biggest gains would be to open up small brick factories that use solar kilns for the bricks.
So the idea is that with some light localized manufacturing we can develop ways to create good housing from local materials and scrap.

Basic Medical Care:

The easiest way to start solving this problem is to take in some of the poorest members of the society and train them as Doctors and Nurses if they agree to help their communities in exchange for their education. Over this Doctors and Nurses who receive a subsidized education could pay it back in the form of a tax either money or working in the poor areas. I know from first hand experience that the medical industry is not designed for the needs of the poor regions a move back to renewable supplies robust equipment etc can greatly increase the quality of medical care in the poor regions we have gone to disposable supplies because its easier then using autoclaves.
I could rant forever on this but the bottom line is with some thought medical care can be vastly improved and equipment and supply costs can be minimized. Local manufacturing of medical equipment could play a large role in this. Next of course decent synthetic labs could produce most of the needed drugs. Lab testing can be reviewed and optimized. I'll stop but the medical profession is so far from whats needed by the worlds poor its in my opinion one of our worst sins. Finally of course birth control and sex education come into play.

Education: Like with Doctors but more tractable its a matter of education of people within the community to be teachers and sending them back to their local communities.
Communal communications with new wireless technologies opens up the chance for almost every part of the world to have equal access to mankinds knowledge. This extends into adult education and practical education. The key point and where I differ from most efforts today is that the educators must come from the community.

Pensions:

This is probably the biggest issue and primary reasons for large families. The first and foremost issue is dealing with single people and widowers. I feel that communal monastic like living arrangements open the doors for people to live a single life for as long as they choose. In the past in most cultures these sorts of communal living arrangements where common often tied to the local religions but the point is that we have removed them in all our cultures with our focus on family living. A family is not the only solution and if we can bring back these alternative ways of life then we can create a population of people that choose to have no children or join the communes with just a few. The problem is of course money and a small global pension would go a long way to helping these types of living arrangements. Pensions can be scaled on the number of children you have with zero receiving a healthy pension. You can argue this for a long time but the key for me at least seems to be communal living arrangements that lessen the need for large families. If enough people choose to have zero children it makes a really big difference. Two people choosing to not have children allows a fairly large family of four to exist without causing population growth. So you can see how its in my opinion what makes the difference not just small families.
Certainly with a social safety net in place and education you can then have smaller families. Finally of course with modern birth control methods being single does not mean you have to risk having a child so it all ties together.

You can break these problems down a number of different ways but the core idea is reintroduction of communal living/collective living for people that are not interested or able to form the traditional family. These same communes could readily be the source for doctors, teachers etc and also be the provider of the pension plan. Done correctly it need not even be a cash issue simply a matter of setting aside sufficient land to allow the commune to support itself.

We should have never ripped these out of our societies I think modern manufacturing and economies of scale is what did them in since light manufacturing was often one of the primary ways these communes continued.

Dignified death? A lot of people are going to be driven crazy with negative life-events, especially those who currently have "wealth" and "status". A lot of them are going to be suicidal.

Another high proportion are more likely to die of hunger, shock, and fatal diseases than by violence.