Indesign sizing/resolution question

The short answer on top of all the prior information — the best of which is Eugene's 'don't overcomplicate it'! — is that a 16:9 layout is paramount, a reasonable amount of resolution for any raster images is probably enough, and the vector nature of all else, including type, passed through PDF, will generate all the image quality you need. (I've done many, many HD presentaions using ID/PDF, since I loathe PowerPoint.)

The only area really needing any extra thought is in images — raster images, photos — where you want maximum screen quality. As long as your source images have an effective PPI of about 200 or more (and ID tells you effective PPI in the Info panel), you probably won't have any issues regardless of how large a screen the pages are displayed on.

Other than that, don't overthink it, don't overcalculate it and don't overcomplicate it. The tech handles the details very nicely in this case. 🙂

Also, Pixels in InDesign are an output Ruler Unit (1/72”) not a measure of resolution—an ID page has no resolution.

The Pixel unit is useful when the Export is to an image format—JPEG or PNG. An Export at 72ppi will result in an image with matching pixel dimensions. PDF is a vector format, so there isn’t much advantage in working with Pixels when the Export will always be PDF.

When you work in InDesign and create a digital document in a pixel format it uses 72 ppi (pixel per inch). Thats why it is so big when you convert it to mm in opposite to if you created the same document in Photoshop using 300 ppi and then converting it to mm. Have in mind that when you create a pixel format the ppi does not really matter. You have A x B pixels, the size will always be that. The ppi defines how this pixel format will be displayed when working in mm or inch which you don't do. So don't worry – 

Whe you place images and know their size is big enough, try checking the files in Photoshop regarding their set ppi. When you set them to 72 ppi (without changing the actual pixel format!) and place them in your digital document in InDesign you should be fine.

When I opened a blank document in Photoshop as 300dpi 1920px x 1080px and convert to mm it's only 162.56mm x 91.44mm which is even more confusing

By @keii24515601

Not sure what's confusing? 

300 Dots Per Inch (dpi) 

1920 x 1080 

1920/300 = 6.4 inches 

1080/300 = 3.6 inches

6.4 inches = 162.56mm

3.6 inches = 91.44 mm

1920px x 1080px in InDesign

Others will correct me on this - but this is my overly simplified version

InDesign operates in 72ppi - and your screen is not 72ppi

1920 px x 1080 px @ 72 - follow same format as above

1920/72= 26.6 inches 

1080/72= 15 inches

But your screen would be actually 92 or 104 ppi or something

I also think acrobat resolution can be set in the preferences

20 you should be working in slightly higher resolution

So increase your photoshop resolution to 92 or 104 or something like that

Ultimately it will rely on the display and the settings you choose.

But don't overcomplicate it.