About PowerPoint to PDF
PowerPoint files are a pain to share. The recipient needs a recent version of Office, or Keynote, or LibreOffice Impress installed. Even then, custom fonts that you used in your deck might not be on their machine, so the text reflows. Animations and transitions that took half an hour to set up don't matter when you're emailing the final deck, but they make the file twice as big.
Converting the deck to PDF strips out the moving parts and pins down the layout. Each slide becomes one page in the PDF, fonts get embedded, and the file size usually drops by half or more.
What carries over
All the slide content. Text, images, charts, tables, smart art, transitions baked into static frames if they had end states. The PDF shows each slide exactly as it looked in PowerPoint's normal view.
Slide notes can come along if you turn that option on. They show up as a smaller section below each slide image, which is the standard handout format presenters use. Off by default since most people are emailing the slide content, not the notes.
Hyperlinks inside slides stay clickable in the PDF. So if your deck linked to a website or another slide, the link works in the converted file.
What gets flattened
Animations and transitions. PDF is a static format, so a slide that builds up bullet points one at a time becomes a single slide with all the bullet points visible. If you need the build sequence, you can split each animation step into its own slide before converting.
Embedded video and audio. The link is removed and the slide shows whatever was on screen behind the player. Better to host the video somewhere and link to it from a static button.
Speaker timings and rehearsed transitions. The PDF doesn't include them. The handout is meant for reading, not for replaying the presentation.
Format options worth knowing
Standard 4:3 slides come out as PDF pages in the same proportion. Widescreen 16:9 (the modern default) gives you wider pages, which prints two-up nicely on landscape A4.
There's an option to fit four slides per page in a handout style, which is the format most conferences print for attendees. Six slides per page is also available for thicker decks where you want a quick reference.
When you'd use this
Sending a deck to an investor or client for review. PDF removes any risk of the slides looking different on their machine, and it's the format every reader app handles.
Sharing conference talks afterwards. Attendees download the PDF, not the PPTX, so they don't need PowerPoint to look at it on their commute home.
Printing handouts. Print directly from the PDF and you'll get the layout exactly as you designed it, with no last-minute font surprises.
Archiving a project deck. Five years from now, the PDF will still open. The PPTX might or might not, depending on what version of PowerPoint exists then.
Picking the right handout density
One slide per page is the default and works for most sharing scenarios. It gives readers room to make notes in the margins and prints cleanly at landscape A4.
Two slides per page is a nice middle ground for review documents. Each slide is still readable from a normal reading distance and you cut your paper usage in half. Good for printed copies that will be skimmed rather than studied.
Four or six slides per page is the conference handout format. Useful when you want attendees to have a quick reference but you don't want to burn through a ream of paper. The smaller slides aren't legible from far away but work fine in someone's hand.