In the PPTX file dies a slide.xml reference or in any way use the slidemaster.xml or slidelayout.xml files?
I ask because this says when you change the master or layout you need to then apply them to any existing slides. That makes me think that the existing slides copy across what they need from the master/layout but don't point to or refer to them.
Our app reads the PPTX to then render it as PDF. If there is no use of the master/layout, then we can ignore those when we read in the slides.
??? - thanks - dave
Slide Masters inherit font and color information from the Theme. Slide Layouts inherit formatting from the Slide Master, Slides inherit formatting from the Slide Layouts.
After a layout has formatted a slide, then you do more work on the slide manually, the slide retains whatever changes you made, but doesn't necessarily reference the layout further. That's why when you update a layout, you often have to select the slide that is based on it and choose Home>Reset to force an update.
Depending on how you're creating the PDF, you may find that the slide doesn't contain all the information you need. As an example, if the presentation has a font theme that uses the Myriad font, the Myriad name will only appear in the theme. The slide master will refer to the theme font as <a:latin typeface="+mj-lt"/> for a Headings font or <a:latin typeface="+mn-lt"/> for a Body font.
A slide layout and the slide based on it will not have any reference to the font unless local formatting has been applied to either to alter the inherited information.