Papier was born in Clanwilliam in the Western Cape. As early as primary school level, he earned provincial colours by representing the at the 2010 Under-13 Craven Week tournament held in Graaff-Reinet. He then moved to Pretoria, where he enrolled at Hoërskool Garsfontein. In 2013, he represented the Blue Bulls at the Under-16 Grant Khomo Week held in Vanderbijlpark, starting all three of their matches and scoring a try in their match against Eastern Province. In 2014, despite still being in the Under-17 age bracket, he was included in the Blue Bulls squad for the Under-18 Craven Week, South Africa's premier rugby union tournament at high school level. He started all three matches at the tournament held in Middelburg, scoring a try in their 36–15 victory over KwaZulu-Natal. After the tournament, he was included in a South Africa Schools team that hosted the Under-18 International Series against their counterparts from France, Wales and England. Papier played off the bench in their 28–13 victory over France in their opening match, but was promoted to the starting line-up for their second match against Wales, scoring a try in their 40–15 victory. He was again used as a replacement for their final match against England, but could not prevent South Africa suffering a 22–30 defeat. Papier had a similar season in 2015; he started all three of the Blue Bulls' matches at the Craven Week in Stellenbosch, scoring a try in their 40–12 victory over his home province Boland. He was once again included in the South Africa Schools squad, this time starting all three of their matches and also being named the vice-captain of the team. He scored a try in their 42–11 victory over Wales, and – after a 12–5 victory over France in their second match – scored another in their 23–16 win over England to avenge their 2014 defeat.
2016–2018: Youth rugby
After high school, Papier joined the ' academy for the 2016 season. Despite not being included in an initial South Africa Under-20 training squad, or a reduced provisional squad named a week later, Papier was included in the final South Africa Under-20 squad for the 2016 World Rugby Under 20 Championship tournament to be held in Manchester in England. He started their opening match in Pool C of the tournament on the bench, appearing for the final eight minutes as South Africa came from behind to beat Japan 59–19. He did not feature in their second pool match, a 13–19 defeat to Argentina, but started their final match, scoring South Africa's first try in the match as they bounced back to secure a 40-31 bonus-point victory over France. The result meant South Africa secured a semi-final place as the best runner-up in the competition, but Papier suffered an ankle injury during a training session, which ended his involvement in the tournament. South Africa faced three-time champions England in their semi-final match, but the hosts proved too strong for them, knocking them out of the competition with a 39–17 victory, and they also lost the third-place play-off match against Argentina, as the South American side beat South Africa for the second time in the tournament, convincingly winning 49–19 to condemn South Africa to fourth place in the competition. Papier recovered from his injury towards the end of the 2016 Under-19 Provincial Championship, starting the ' final two matches of the regular season. He scored a try in the first of those, a 62–7 victory over, before he helped the Blue Bulls secure second place on the log with a 50–30 victory over. He also started their semi-final match against, but a 34–24 victory for the team from Johannesburg ended the Blue Bulls' participation in the competition. In November 2016, Papier was named in the Super Rugby team's extended training squad during the team's preparations for the 2017 Super Rugby season.
