Firstly - just want to back @Just-B and that info is very good and follow it.
Secondly - youâre doing the exact correct thing to export the poster to PDF from PSD. Thatâs a very good workflow to get the file to the right people.
Thirdly - it depends on what settings youâre using in reducing the PDF.
Or is it just the blanket - reduce pdf size?
Now:
To keep your Vector layers, things like, text layers, vector masks and vector shapes from Photoshop - you need to keep these as live text layers, and do not rasterise them.
By rasterising them you are reducing the text (live text which is Vector) to a pixel (which is raster) - so itâs rasterising the text to the native resolution of the PSD file.
If the native resolution of the PSD file is high enough - the text should be ok - but typically when RIP rasterises text it rasterises it to 2400 - which is a lot higher than the faux-300 that is bandied around.
So what happens when you flatten your Live Text (text layers) and vector shapes/vector masks in Photoshop.
They become raster - and your resulting PDF is the same resolution - so reducing the file size in Acrobat will likely not have any affect.
As itâs already - for example - set to 300.
So youâd need to reduce the overall resolution which would impact the text quality.
So my first port to reduce a PDF size would not to use the Reduce File Size - as I believe this only removes header information from a bloated PDF - or change the PDF setting from different versions.
Adobe have a help page about this
https://helpx.adobe.com/ie/acrobat/using/optimizing-pdfs-acrobat-pro.html
Basically - yes Reduce File Size shouldnât affect quality of the PDF - as it optimises the PDF and only affects images for resolution, and vectors can be left alone, as thereâs nothing to optimise.
But, sometimes, to reduce file size - the embedded font information may be stripped.
Which is probably why youâre seeing wonky text when rotating - perhaps.
Instead - Iâd use PDF Optimisation - which is in the link I shared with you.
Itâs a bit more complicated - but with some experimentation you can get there easily.
Iâd say because the font cannot be embedded in PDF - can you tell us the name of the font - whether it was bought or downloaded for free?
If itâs a free font itâs typically not allowed to embed the fonts in PDFs - which is why the text gets scrambled - or basically Acrobat is substituting the font as there is no embed info and the font cannot be used.
You could/should purchase the font you want to use - or contact the font vendor to see if there is a version you can use.
I wouldnât have gone this way - if you started in Illustrator - you could link the images rather than working with them directly in Illustrator.
That way - you can edit the image in Photoshop - and update the link in Illustrator.
You can then apply your text (live text/vector text) all your vector info etc can be applied in illustrator along with the photo/raster elements.
And you can save to PDF directly from Illustrator - which would give you the best quality output.