Short answer: Perplexity can't read your PDF for one of five reasons: the file is over 40 MB, you've used your weekly upload allowance, the file is long and Perplexity read only "the most important parts", scanned pages didn't come through, or the PDF sits behind a login. Perplexity is an answer engine first: it's built to search the web and treats your file as one more source, which explains most of these limits.
Cause 1 - The file is over 40 MB
Perplexity's help centre is clear: "File size is limited to 40 MB for all file types." High-resolution scans and image-heavy reports pass that quickly.
The fix: compress the PDF or split it into parts, and attach the part you need.
Cause 2 - You've used your weekly upload allowance
Uploads aren't unlimited on Free, Pro or Max. Each plan has an allowance that resets on a rolling weekly basis, and Max's is higher than Pro's. Images you attach or paste into a search count toward it, and so do files attached from connected apps like Google Drive. When it's used up, Perplexity shows a pop-up as you try to attach; on Pro it may suggest upgrading to Max. Perplexity notes that this "does not mean file uploads have been removed from your plan".
There's no reset day: each upload stops counting about one week after you attached it, and your remaining allowance isn't shown in account settings.
The fix: wait for older uploads to roll out of the window, or paste the text you need instead of attaching the file.
Cause 3 - The PDF is long, so Perplexity read only part of it
Perplexity says short files "can be analyzed in their entirety", but "if you upload a long file, Perplexity will extract the most important parts to provide the most relevant response to your query." That's sensible for a quick question and a problem for a detailed one: if the answer you need is in a section that wasn't extracted, Perplexity answers without it.
The fix: name the section, chapter or page you're asking about, or split the PDF and attach only the relevant part. Check important answers against the document.
Cause 4 - Scanned pages didn't come through
Perplexity accepts PDFs and images, but its help centre doesn't say how it treats image-only pages inside a PDF. If the answer ignores what's on scanned pages, those pages weren't read as text.
The fix: run the file through OCR so it has a real text layer, using our guide to making a PDF searchable, or upload the key pages as images.
Cause 5 - The PDF is behind a login, or in another thread
Perplexity can't open files behind your company login, and a file's context is kept for follow-up questions "within that session". A new thread doesn't automatically know about a file you attached elsewhere.
The fix: download the file and attach it, or connect the source app if your plan supports it, and keep follow-up questions in the same thread.
Perplexity's file limits at a glance
From Perplexity's "File Uploads" help article, last modified 7 September 2026:
| Limit | Value |
|---|---|
| File size | 40 MB, all file types |
| Upload count | Rolling weekly allowance on Free, Pro and Max (Max higher) |
| What counts | Attached files, pasted images, files from connected apps |
| Long files | Most important parts extracted |
| File types | Text, code, PDFs, images, audio and video |
| Audio and video | Speech transcribed; visual scenes not indexed |
Reading the whole PDF, with citations
When the document matters more than the web, an in-browser reader is the better fit. Sidenote reads the PDF you have open, including files in Drive, SharePoint or an email, through your own signed-in session and read-only. Long documents are indexed in full and each question retrieves the relevant passages, scanned pages are OCR'd on paid plans, and every answer carries a citation that scrolls the PDF to the exact sentence. Claims that can't be matched to a passage are dropped server-side.
Perplexity vs an in-browser PDF reader
| Perplexity | In-browser reader (Sidenote) | |
|---|---|---|
| Built for | Answering from the web | Reading and questioning documents |
| File limits | 40 MB; weekly upload allowance | Reads the open file, no upload step |
| Long documents | Most important parts extracted | Indexed in full |
| Files behind a login | Download and attach | Read in place, read-only |
| Verify an answer | Check the PDF by hand | Click a citation to the exact sentence |
For the full comparison, see Sidenote vs Perplexity.