Generally yes, but more details are needed.
What version of Premiere Elements are you using and on what computer operating system (including 32 or 64 bit) is it running?
Are the video file types supported by the version of Premiere Elements and computer that you are running it on?
Premiere Elements (any version) allows for one project preset and that project preset should match the properties of your source media so that the program is directed to set up the correct space in the monitor for editing purpose. So, a mixed Timeline can be challenging and priorities need to be set. Here I am targeting frame size. So, if you have a 1920 x 1080 and 720 x 480, you pick one project preset (1920 x 1080 or 720 x 480) as per the preset's description, and you could scale in the monitor the one that does not match the project preset's frame size.
If you are talking about using files with different video and audio compression and file extensions (compression types: H.264, AVCHD, Windows Media Video 9, etc with file extension types: .mov, .mts, .avi, .wmv, etc), the general answer would be can do. But from my point of view, the answers are in the specific details of what is involved in the properties of those videos.
If you do not already have Premiere Elements and are considering doing so, I would suggest that you download and install the free 30 day tryout of Premiere Elements (version 11 at this time) to see if it works for you.
Please review the above and then let us know if we have targeted your question.
I am using Prem Elements 11
Windows 7 64bit
I am making a birthday movie and all contributors have sent me different filetypes / sizes / frame rates
I think all are supported by Windows except one which only played on VLC Media player (this one was named as "xxx.MOV - Google Drive.flv" )
Mostly mp4 but at 4 different sizes !
Several MOV files - 2 different sizes
m4v file at a completely different size
I tried converting the flv file to mp4 - the video converted fine, but the sound vanished.
I would be most grateful for a steer in the right direction ... I'm a fast learner - but my expertise has been mainly with stills not video