What size is the source file?
What size is the Sequence?
Whatever..NO... is the probable answer !
Flash would be the correct program for working with SWF files.
I guess that working in Flash is the way to go, but every time in a Mac I export to Quicktime from Flash CS5 with any setting, the files came with lots of artifacts, and if I change the output size it pixelates, so I don't know other way.
Is there a way to import into Premiere an SWF file and do something similar to the "continuous rasterize" from After Effects, in order to allow scaling it to a bigger size without pixelation?
What is your output goal? That will help you decide between Flash vs a video editing/compositing program.
Why not use AE?
Are some of the elements in the swf not vector based? For example, the swf could contain an flv element.
every time I export to Quicktime
So don't export to Quicktime.
Do you have After Effects? If so, we can suggest ways to do the scaling that you need to do in After Effects and then use the result in Premiere Pro.
You can skip ahead and anticipate the answer by looking at these ways to move things between After Effects and Premiere Pro.