You are about to send a PDF to a professional print shop, and they have asked for vector graphics wherever possible. Or you need to enlarge a logo from a PDF for a banner, and you need to know whether it will pixelate when scaled up. Knowing whether the images in your PDF are vector or raster determines how they will behave at different sizes and on different output devices. A vector graphic scales to any size without quality loss. A raster image becomes pixelated when enlarged beyond its native resolution.
The distinction between Raster Vector PDF content matters for any print project, but it is also important for screen display at high resolutions, for accessibility where vector text can be read by screen readers, and for file size where vector graphics are typically much smaller than equivalent high-resolution raster images.
The Fundamental Difference Between Vector and Raster Content
Raster images are grids of colored pixels. A JPEG photograph, a PNG screenshot, a scanned document, each of these stores color values for every pixel in a rectangular grid. When you enlarge a raster image, the software must invent new pixels to fill the gaps, a process called interpolation that produces blurring or visible pixelation. Raster images have a fixed resolution measured in pixels per inch, and their quality is bounded by that resolution.
Vector graphics are mathematical descriptions of shapes. A circle is described by its center point and radius. A line is described by its endpoints. Text is described by character codes and font references. When you enlarge a vector graphic, the software recalculates the shapes at the new size with perfect sharpness. Vector graphics have no fixed resolution. They render at the maximum quality the output device can produce.
The zoom test alone answers the question in under five seconds for most documents.
Most PDFs contain both types of content. Photographs are raster. Text is vector. Logos can be either, depending on how they were created and embedded. Diagrams and charts are usually vector if created in illustration software, but they become raster if they were screenshotted and pasted in rather than embedded as native graphics.
Visual Methods to Identify Vector vs Raster Content
The simplest test is the zoom test. Open the PDF at 400 or 800 percent zoom and look at the edges of the graphic in question. Vector edges remain perfectly sharp at any zoom level. Raster edges become visibly jagged or blurry as the individual pixels become visible. This test takes seconds and requires no special tools, only a PDF viewer with high zoom capability.
A second visual test uses the selection tool. In most PDF viewers, try to click on the graphic. Vector text can often be selected character by character. Vector shapes may be selectable as individual objects. Raster images select as a single rectangular block because the viewer treats the entire pixel grid as one object.
For PDF Quality assessment of logos specifically, look at the logo edges where they meet the background. A vector logo has hard, clean edges regardless of the logo complexity. A raster logo has anti-aliased edges where pixels of intermediate color smooth the transition between the logo and the background. At normal viewing size, these anti-aliased edges can look cleaner than vector edges, but at print resolution they become visibly soft.
Technical Methods for Content Type Detection
Adobe Acrobat includes a tool specifically for this purpose. Open the Print Production panel and select Output Preview. In the preview window, enable the Object Inspector and click on the graphic. The inspector reports the object type, resolution if raster, and color space. This is the most reliable method for professional print preparation.
For users without Acrobat, most PDF viewing and editing applications provide a document properties or document information panel that lists the image formats used in the file. If the panel lists JPEG, PNG, or TIFF, the document contains raster content. If it lists only font names and vector paths, the content is vector. This check is less precise than the object inspector but available in more tools.
A third method extracts all images from the PDF to a folder. Open the extracted images in an image viewer and check their format and resolution. Vector graphics do not extract as images because they are not stored as pixel data. If a logo extracts as a 150 DPI JPEG, it is raster. If it does not extract at all, it is likely vector.
WukongPDF can help prepare PDFs for PDF Printing by processing the file through the browser, where you can inspect page elements and identify content types before sending the document to a print service.
What to Do When Critical Graphics Are Raster
If a logo that must be printed at large size turns out to be raster and low resolution, several options can rescue the situation. Contact the original designer and request the vector source file, typically an AI, EPS, or SVG file. Replacing the raster logo with the vector original is the best solution.
If the original file is not available, vectorization tools can trace the raster logo and convert it to vector paths. The quality of the conversion depends on the logo complexity. Simple logos with solid colors and clean shapes trace well. Complex logos with gradients, shadows, or photographic elements trace poorly or not at all. Vectorization is a last resort, not a first choice.
If neither replacement nor vectorization is possible, upscale the raster image using AI-powered upscaling tools before placing it in the PDF. These tools add plausible detail that can make a low-resolution image acceptable at a larger size. The result is not true vector quality but may be good enough for non-critical applications.
The file size of a PDF can provide a clue about whether its graphics are vector or raster, though it is not a definitive test. A single-page PDF that is 500 kilobytes is likely mostly vector. A single-page PDF that is 15 megabytes almost certainly contains high-resolution raster images. Large raster images dominate file size in a way that vector graphics do not.
When preparing a document for commercial printing, the print shop will specify minimum resolution requirements for raster images and may require vector graphics for logos and text. Meeting these requirements before submitting the file avoids production delays and additional charges for file preparation. A quick content type check using the methods described here confirms whether your file meets the printer specifications before you send it.
Some PDF creation tools embed both vector and raster versions of the same graphic. The vector version is used for on-screen display and high-resolution printing. The raster version serves as a fallback for viewers that cannot render the vector content. This dual representation increases file size but provides compatibility across a wider range of viewing environments.
The resolution of raster images embedded in a PDF is determined at the time the PDF is created. Changing the resolution after the fact requires re-exporting the PDF from the original source document with different settings. No PDF editor can increase the true resolution of a raster image, though some can apply sharpening filters that improve perceived sharpness without adding real detail.
For PDFs that will be used in both print and web contexts, consider maintaining two versions: a high-resolution version for print with raster images at 300 DPI and vector graphics preserved, and a web version with raster images downsampled to 150 DPI. The print version ensures quality for physical output. The web version ensures reasonable file size for download and on-screen viewing.
Designers who receive logos from clients in PDF format, verifying whether the logo is vector or raster determines whether it can be used for large-format printing. A client who sends a raster logo at 72 DPI embedded in a PDF may not understand why it cannot be printed on a trade show banner. Being able to demonstrate, by zooming into the PDF and showing the pixelation, helps the client understand the limitation.
PDF files created by different design applications have different tendencies toward vector preservation. Adobe Illustrator and InDesign preserve vector content well when exported with the correct settings. Canva and similar browser-based design tools often rasterize vector elements during PDF export because their internal rendering engines are optimized for screen output rather than print production.
Print service providers typically require raster images at 300 DPI at the final print size. A logo that appears at 2 inches wide in the PDF and is embedded as a 600-pixel-wide raster image has an effective resolution of 300 DPI at that size, which meets the requirement. The same logo enlarged to 6 inches wide would have an effective resolution of only 100 DPI, which falls below the print standard. Calculating the effective resolution at the intended print size before sending the file prevents quality surprises.
Vector content in PDFs is sometimes stored as embedded PostScript or EPS fragments, particularly in PDFs created from older design software. These fragments are not standard PDF vector paths and may not render correctly in all PDF viewers. If you encounter a PDF where vector content appears differently in different viewers, check for embedded PostScript fragments using a PDF structure inspection tool.
| Detection Method | How It Works | Reliability | Tools Needed |
|---|---|---|---|
| Zoom test (400-800%) | Vector stays sharp; raster shows pixels | High for obvious cases | Any PDF viewer |
| Selection test | Click graphic; vector text is selectable | Medium; some vector not selectable | Any PDF viewer |
| Object inspector | Reports object type and resolution | Highest; definitive answer | Adobe Acrobat Pro |
| Image extraction | Extract all images; vector does not extract | High for raster confirmation | PDF tool with extract feature |