Should I try lossless compression first?

Yes, if keeping selectable text matters. Compress PDF in Lossless mode keeps everything; use this preset when the limit is strict.

Are my PDF files uploaded?

No. The document is opened and rewritten inside your browser. It is never sent to a server, and closing the tab discards it.

JavaScript is turned off. InspireTools processes files in your browser, so the tools need JavaScript to run.

Shrink a PDF to under 2 MB for email and upload limits.