How to convert iPhone photos to PDF
Open HEIC to PDF in Safari, tap to pick your photos, press Start and save the PDF to Files.
On your iPhone
Tap Choose files, then choose Photo Library. Your iPhone may convert photos to JPG as it hands them over. If it does, use JPG to PDF instead.
On a Windows PC
Copy the .heic files over, then add them here. You don't need any HEIC extensions, because the browser does the decoding.