What is the maximum allowed size for a SQLite database in a Windows Forms application?
Can I use PetaPoco as an ORM, or can you suggest a similar ORM?
Concerning your max size question the limit is about 14 terabytes (http://www.sqlite.org/limits.html).
And I think you can use PetaPoco, since this lines can be found in PetaPoco.cs:
enum DBType
{
SqlServer,
SqlServerCE,
MySql,
PostgreSQL,
Oracle,
SQLite
}