You can now copy text directly from an opened PDF in Snip. Hover over any line in the PDF (text or math) to reveal a copy to clipboard button to the left of the line:
You can also click and drag to highlight a region of interest (i.e. multiple lines) or double click any line to get access to selectable and copyable text or LaTeX. By default, all math will be copied as inline or block mode LaTeX. The copy from PDF feature works for printed and handwritten PDFs.
Watch this video below to see how to use this feature in the Snip web app: