From Bulbapedia, the community-driven Pokémon encyclopedia.
The Pokémon News Press (Japanese: ポケモンしんぶんしゃ Pokémon Newspaper Company) is a small building located in Solaceon Town. It is run by two people, who create and print the Sinnoh region's newspaper. The Pokémon News Press is tiny, containing only a TV and a desk, with a writing pad and a computer, but the newspaper has many fans. One of the men asks the player each day to show him a different Pokémon the player has already seen, awarding Poké Balls if the request is granted. In Platinum, he will also award a Heart Scale for showing a Pokémon.
There are featured top stories of the newspaper on the computer called the "Weekly Poké Ball Roundup". They are featured articles on new types of Poké Balls:
"Dark caves and streets unlit at night are forbidding places to go. If you're threatened by the dark, a supply of Dusk Balls is your biggest ally! Use them in the dark for the best Pokémon-catching performance! Keep the dark at bay on your travels with Dusk Balls!"
"Catching Pokémon is best accomplished by whittling the target's HP down as low as possible, then tossing a Ball. But a Pokémon caught that way can't be used in battle right away. That's where the Heal Ball comes in handy. You can lower the target's HP bar to red, put it to sleep, or paralyze it. The Heal Ball instantly heals whatever ails the Pokémon it catches! That's the Pokémon-friendly Heal Ball! Please, do give it a try!"
"When attempting to catch a Pokémon, you want to cut the target's HP. But a fleet-footed Pokémon could bolt if you take too much time. The Quick Ball is the solution to that dilemma. It's designed to work best when thrown right at the start of battle! The Quick Ball: the perfect gift for the impatient Trainer!"
"The Pokémon of the mothering sea aren't like the others. If you are brave enough to face such intimidating Pokémon, the Dive Ball is perfect for you. For Pokémon you meet in the sea, and for Pokémon caught fishing... The Dive Ball is the Poké Ball you can count on!"
There is a news reporter at the desk writing an article about a certain Pokémon. He wants a "Pro Pokémon Catcher" to help him write the article by giving him the certain Pokémon to see. The man asks the player each day to see a different Pokémon in order to write his article. The Pokémon he asks for are always Pokémon that the player has already seen or caught. The player has until the end of the day to catch and show him the chosen Pokémon he asks for. In return, he randomly awards the player with three of one type of these kinds of Poké Balls:
All types of the Poké Balls available in the Sinnoh-based games are available, except for Master Balls, Premier Balls, Cherish Balls, Safari Balls, and Park Balls.
This is the only way to obtain Dive Balls in Diamond and Pearl without using Pal Park.