When uploading PDF files to your Elicit Library, we recommend uploading in batches of 100 or fewer papers to maintain the speed of the uploads. If your PDF files are particularly long or complex, then we would recommend smaller batches. There is no limit on the number of PDFs your library can hold at this time.
Uploading papers to your Library doesn't use any of your monthly usage unless you have Premium PDF Parsing enabled on your Settings page. See Usage limits in Elicit.