I do not know if it's correct function, but the idea is to use different page sizes in a single file in LO Draw. Currently this severely limits the functionality of Draw, as the ability to create collections of shapes or layout documents requiring different page sizes or simply change their page orientation. This involves using more than one file to a project. On the other hand help to improve the import of PDF files. (Bug 92948)
Bug 92948 is resolved for LO 5.0+
Better case regards PDF handling is bug 64990.
But, this is duplicate of bug 49787.
*** This bug has been marked as a duplicate of bug 49787 ***