Allori joins from Italian side Benetton Treviso and played in all six of their Heineken Cup matches this season following spells at French clubs Brive and Tarbes.
Newlands has previously played for Kelso and Heriot's and was an apprentice at Borders.
Edinburgh head coach Lynn Howells said: "Augusto will strengthen the loose-head position which is what we were looking to do.
"And as he has competed in Europe this year, he will give us the experience we need at this high level.
"He gives us a degree of flexibility as he is able to play all positions in the front row, but is a specialist loose-head prop."
Howells added regarding Newlands: "Scott is a big, abrasive back-row forward.
"He is aggressive in the contact area, hits above his weight, and his height in the line-out gives us options in the back row.
"He will also be available through the World Cup and Six Nations."