Define "the Aperture files".
Read this concise guide.
The files you imported into an Aperture Library can be exported (at any time, and repeatedly) using the command "File ▹ Export ▹ Originals". Your Originals are never altered. What went in is what comes out.
Adjustments and changes to the metadata that you made since creating an Image in Aperture by importing a file are saved to a text file. This file is combined, on-the-fly, with the Original to create the Image that you see in Aperture. There is no file saved to disk that is the full-size Image. Thumbnails are saved, and Previews are saved. These are JPG files, almost always smaller than the Original. They are not substitutes for the Image for the use you have.
When you need a file of an Image to use in another program, you export the Image from Aperture. "Export" means "Make me a file of this Image according to these file specs I'm providing". The way to get files of your adjusted Images is simple: create them by exporting. Specify "Original size", and use a loss-less image-file format (e.g. TIFF 16-bit) if you want to retain as much visual information as possible.
Search the Web for information about transitioning from Aperture to Lightroom. Note that I say "transitioning". You cannot move a database from one format to another without significant changes, and likely some loss of information. Adobe provides a tool and some instructions. I strongly recommend working out the process step-by-step, and then proceeding with first a few Images, then a bushel-ful, and stopping to use the first few, the the bushel-ful, before committing your entire collection to the process.
As always, never use any computer file without having a back-up.
We have seen mixed reports here of the success of the LR tool that creates a LR database from your Aperture database.
If you want to carefully define the process, and test and refine it, use the excellent process-development, analysis, and execution program inShort.
Sadly, there is not and can never be a good, thorough re-positioning of the digital assets in your Aperture Library to become digital assets in a LR database. Just as a metaphor for any user contemplating transitioning to another digital asset manager: that would be like digging up a house in one country, planting it in a hole in another country, and expecting to be able to use the toilet and the sinks, turn on the lights, cook dinner, and sleep soundly.
HTH,
Kirby.
