"At the beginning of this process, we set out the four areas where we wanted to see substantial change, and this document delivers that," he told reporters.
"But of course there's still detail to be worked on, there's important things to be secured, there's further work to be done."
The document, released by European Council President Donald Tusk on Tuesday, grants concessions in key areas being sought by Cameron, as he works to secure more favorable conditions of the country's EU membership ahead of a planned British referendum on whether to stay or leave the 28-member union.
Among the proposals are measures that would allow the UK to suspend welfare benefits to migrants from the EU for up to four years, and provisions whereby member states can block unwanted EU laws.
Other gains for Cameron include new rules to stop non-EU migrants from entering the UK through "sham marriages" to EU citizens and greater protection for countries, such as Britain, that do not use the euro as currency.
Tusk: 'Good basis for a compromise'
In a letter released alongside the document Tuesday
, Tusk said that the plan "goes really far in addressing all the concerns raised by Prime Minister Cameron."
"The line I did not cross, however, were the principles on which the European project is founded," he wrote.
He believed the proposal was "a good basis for a compromise," he wrote.
In recent days, Cameron has been holding urgent talks with Tusk, who leads a body made up of the heads of the European Union
's member states, to thrash out plans to reform the terms of the UK's EU membership in hopes of avoiding a potential "Brexit," or British exit, from the union.
Cameron has been seeking significant changes to the terms of Britain's European Union membership, in terms of social benefits and migration, sovereignty, economic governance and competitiveness.
The British referendum on whether to leave the EU will be held some time before the end of 2017, most likely this year.
Both sides have been seeking to reach an agreement so a proposal can be presented at a key summit next month before European leaders, who will need to grant their approval.
Halt on benefits
A key sticking point in discussions has been the eligibility of new migrants from the European Union to the UK to receive welfare benefits.
Cameron has sought rules preventing EU citizens working in Britain from claiming "in-work benefits" -- such as income supplements for those in low-paid work -- for four years, as part of efforts to reduce migration from the EU into the UK.
Other European countries have been opposed to this, saying it is discriminatory and runs counter to the EU's guiding principle of freedom of movement.
The draft deal proposes creating a so-called emergency brake mechanism that could be applied when countries experience an "inflow of workers from other Member States of an exceptional magnitud