A vector PDF stores a drawing as lines, arcs, curves and text, the way CAD and BIM programs draw them. A raster PDF stores it as a grid of pixels, like a photo or a scan. Drawings exported directly from AutoCAD, Revit, and ArchiCAD are vector: sharp at any zoom, searchable, and measurable by snapping to real lines. Scanned drawings and "printed to image" drawings are raster: they blur when you zoom in and their text cannot be searched without OCR.
Vector vs raster PDF at a glance
| Vector PDF | Raster PDF | |
|---|---|---|
| Stored as | Lines, curves, fills and real text | Pixels (an image) |
| Typical source | Export or plot from CAD/BIM | Scanner, phone photo, "print as image" |
| Zooming in | Stays sharp at any zoom | Becomes blurry or blocky |
| Text | Searchable and selectable | Not searchable without OCR |
| Measuring | Can snap to line ends and corners | Only by clicking on the image |
| File size | Small for simple drawings, large for very dense ones | Grows with page size and resolution |
| Layers | Can keep CAD layers | No layers |
How to tell if a PDF is vector or raster
- Zoom in far on a thin line or small text. Vector stays crisp; raster turns into pixels.
- Try to select or search text. If a word from the title block cannot be found, the page is probably raster.
- Look for layers. A PDF with a layers list was almost certainly exported from CAD.
- Many PDFs are mixed: vector linework with a raster site photo or a scanned survey underneath.
Why vector drawings can still be heavy
A vector drawing is not automatically light. A plan with hatching, furniture blocks, detailed site survey linework and xrefs can contain over a hundred thousand separate paths on one sheet, and every one has to be drawn each time you zoom or pan. That is why some vector sets feel slower than a scan of the same sheet in many PDF viewers. Common reasons a CAD export gets heavy:
- Dense hatch patterns exported as thousands of individual lines
- Exploded text (every letter as outlines instead of a font)
- Xrefs and survey data with far more detail than the sheet shows
- Embedded high-resolution images or rendered backgrounds
More on this in why is my PDF so slow with construction drawings and exporting DWG to PDF for review.
Which should you send?
Send vector whenever the drawing comes from CAD or BIM. It is sharper, searchable, measurable, and usually smaller. Raster is only right when there is no vector source (a scanned archive drawing, a marked-up print photographed on site) or when you deliberately want a flattened copy that cannot be edited. If you need to send a raster version, keep the vector original as the master.
Working with both kinds in one PDF editor
Ncored, the PDF editor we built in our architecture studio, is built for heavy vector sets exported from AutoCAD, Revit, and ArchiCAD: they open fast and stay smooth on scroll, zoom, pinch and pan on Windows and Mac. Scanned and image-heavy pages render cleanly too. Measurements snap to the drawing's own vector lines (corners, line ends and crossings), and on a scan you can calibrate the scale against a known dimension and measure by clicking. Ncored does not do OCR, so text on a scanned page stays unsearchable. See marking up scanned blueprints.
Frequently asked questions
Is a PDF vector or raster?
It can be either, or both. A PDF is a container: exports from CAD are usually vector; scans are raster; many drawings mix both.
Can a raster PDF be converted to vector?
Only by tracing, either by hand or with raster-to-vector software, and the result always needs checking. It is not a lossless conversion.
Why does my vector PDF look blurry?
Usually because part of it is an embedded image, or because the viewer is still drawing a low-resolution preview while it renders the full detail.
Does vector or raster print better?
Vector prints sharper at any paper size. Raster prints well only if its resolution matches the paper size, roughly 300 dpi for line drawings.
Related: how to convert PDF to DWG in AutoCAD, PDFs with layers, open a large construction PDF.
Further reading: how to turn PDF layers on and off, can AI read construction drawings.