PDF has outlived a lot of formats that were meant to replace it, and for one reason: it's the only common format where what you send is what they see.
That's the whole argument. A Word file, a Google Doc, a Pages document, all of them re-render themselves on the recipient's machine using whatever fonts it happens to have. Your carefully spaced quote arrives with the total pushed onto page two and a font you've never chosen in your life. A PDF carries its fonts and layout inside the file, so it looks the same on your laptop, their laptop and their phone.
Getting one out of whatever you're using
From Word, use File then Save As and pick PDF, or File then Export. Google Docs is File, Download, PDF Document. Excel and Sheets export the same way, though check the page breaks first because spreadsheets love to split a table across four pages.
On a Mac, the print dialog has a PDF button in the corner and it works from nearly any application, which is the fastest route when a program has no obvious export. Windows has the same trick as a printer called "Microsoft Print to PDF". Phones do it too: the share sheet on iOS will usually offer to print, and printing to PDF is one tap from there.
None of this is hard. The problems come afterwards.
The things that go wrong
Fonts are the big one, and the fix is to embed them, which most exports do by default. It's worth opening the finished PDF and looking at it, because a substituted font is obvious once you see it and invisible if you never check.
Size is the second. If your two-page quote is 12MB, an image is doing that, almost certainly a logo saved at print resolution or a photo straight off a phone. Resize the images before you place them, or export at a lower image quality. Nobody's email is grateful for a 12MB attachment.
Then there's the mistake that costs money: exporting the wrong version. Once a PDF exists it's a snapshot, so if you tweak the price in the original afterwards, you now have two documents that disagree and no way to tell them apart from the filename. Name your files so you can tell, and never send a PDF you exported before the last edit.
What PDF does not do
PDF is not a lock. This surprises people, because the format feels final in a way a Word file doesn't.
Anyone with the right tool can edit a PDF, including one that's already been signed. The signature image stays exactly where it was while the figure above it changes. If the integrity of a signed document matters, the protection has to come from a signing process that seals the document and records its state, not from the fact that it's a PDF.
Which is worth knowing before you build a workflow on export-and-email.
Where the exporting stops being the point
Notice how much of the above is work you're doing every time you quote someone. Open last month's document, change the client name, change the numbers, hope you caught every reference to the old job, export, check the fonts, attach, send, then chase the signature.
That loop is what E·BIZI Papers replaces. You design the quote or contract once as a template, fill in what changes, and it produces the finished PDF and collects the signature through a link you email to the client. No exporting, and no version of the document that disagrees with the one you sent.